K Element & Ors v Tesco Stores Limited [2025] EAT 145

[2025] EAT 145

Case No EA-2025-000486-AT

Case No EA-2025-000487-AT

EMPLOYMENT APPEAL TRIBUNAL

Venue Rolls Building, Fetter Lane, London, EC4A 1NL

Date 9 October 2025

Before

THE HONOURABLE MRS JUSTICE STACEY DBE

Between

Ms K Element & OthersAppellant

(all Claimants represented by Leigh Day and HarcusAppellant

Parker Employment)Appellant

- and –

Between

Tesco Stores LimitedRespondent

Betsan Criddle KC, Andrew Blake and Stephen Butler (instructed by Leigh Day and Harcus Parker Employment) for Appellants

Tom Coghlin KC and Mark Greaves (instructed by Freshfields) for Respondent

Hearing Hearing date: 5 June 2025

JUDGMENT

[1]This appeal concerns the narrow question of the granting of permission for a party to adduce expert evidence from an economist at a Material Factor Defence hearing in the Employment Tribunal in an equal value claim. It arises in the context of long running equal pay litigation pursued by mostly female shop-based employees against their employer, Tesco Stores Ltd. They compare themselves to the predominantly male staff at Tesco’s distribution centres (“DCs”). There are now over 50,000 claimants involved in the proceedings. The litigation has been hard fought at every step of the way since proceedings were first lodged in 2018. Progress in the case has been frustratingly slow as has been frequently commented on by this appeal tribunal in the many appeals against interlocutory and preliminary decisions of the Employment Tribunal (see for example HHJ Tayler in Tesco Stores Ltd v Element

[2025] EAT 26

, at [3] and Kerr J in Tesco Stores Ltd v Element

[2024] EAT 83

at [69]).

[2]I shall continue to refer to the parties as they are before the tribunal with Tesco Stores Ltd as the respondent and Ms Element and her colleagues as the claimants. The claimants are represented by two sets of solicitors, Harcus Parker and Leigh Day, and where necessary I shall refer to them as the Harcus claimants or the Leigh Day claimants, but for the purposes of this appeal the two sets of claimant litigants combined forces and I heard only from Ms Criddle KC instructed jointly by Leigh Day and Harcus Parker Employment who was acting for all the claimants on this occasion.

[3]It is not necessary for the purposes of this judgment to set out a full chronology of the procedural history of the litigation to date. But in brief outline summary in so far as is relevant to this appeal, the claims are for work of equal value. The process of job evaluation has started under the Employment Tribunal (Equal Value) Rules of Procedure 2013 New procedural rules are now in force contained in Schedule 2 to the 2024 ET Rules of procedure, but the material provisions relevant to the issues in this appeal are unchanged from the 2013 EV Rules. for the first of three tranches of sample claimants and their named comparators with a stage 3 hearing scheduled for 2027. A number of Employment Tribunal judgments arising out of the stage 2 equal value hearings are currently under appeal before this tribunal and the Court of Appeal.

[4]Initially the equal value question for the tranche one sample claimants was to be determined at the prior to issue of whether the respondent could rely on any material factor defences (“MFDs”) to explain or, if necessary, objectively justify the differences in pay between the claimants and their comparators, with the result that the sex equality clause in the claimants’ terms would have no effect pursuant to s.69 Equality Act 2010 (EqA 2010). But at a preliminary hearing on 21 March 2024 (“the 21 March 2024 PH”) the Tribunal acceded to an application by the claimants (contested by the respondent) to consider the MFD issues prior to the equal value issues. At the 21 March 2024 PH the tribunal also made a number of other various directions and listed a hearing for the MFD issues to take place before the final equal value hearing in the autumn of this year. The respondent has unsuccessfully appealed orders made at the 21 March 2024 PH and was given short shrift by Kerr J in Tesco Stores Ltd v Element & Ors

[2024] EAT 83

on 24 May 2024.

[5]The substantive MFD hearing scheduled for this autumn has had to be postponed because of this appeal and has now been listed to take place over eight weeks from 16 to 23 March and 1 May to 10 June 2026.

[6]After the EAT had rejected the respondent’s appeal from the 21 March 2024 PH, by letter to the tribunal dated 29 November 2024, the respondent applied for permission to adduce expert economics evidence in support of its MFDs on the relevant labour markets for stores colleagues and DC colleagues, the market prices and the competitiveness within those markets (the Markets Issue”) and the consequences of the respondent paying stores colleagues more than it did (“the Consequences Issue”) and on a third issue that is no longer in dispute between the parties. The application was opposed by the claimants and after a hearing on 9 December 2024 in a judgment sent to the parties on 23 December 2024 (“the First Expert Evidence Decision”), two of the three applications by the respondent were refused by the tribunal and the third was agreed between the parties. The agreed matter was that the parties would jointly instruct an expert to assist the tribunal to understand the statistics produced by the respondent’s “Unipay” system for holding pay and other HR data that could be used for summarising and presenting the data from Unipay to identify the make-up of advantaged and disadvantaged groups, including by job role, full-time or part-time status and union check off status to prepare so-called “Bailey tables”.

[7]In relation to the two contested matters - the Markets Issue and the Consequences Issue - the EJ concluded that expert evidence was not reasonably required to resolve the proceedings [46] and refused the application. He further found that if expert evidence from an economist might reasonably have been thought to be required then he would have concluded that its weight would not be sufficient to justify permitting its admission. It was not a matter for expert evidence, but for the witnesses of fact from the respondent, such as the Chairman, Chief Executive and Finance Director and other board members and senior staff, to give evidence of the effect on the respondent of the need to pay more to its stores staff as a result of a judgment in favour of the claimants, not expert economists. The evidence of the experts would be speculative and no better than the evidence of the respondent’s own senior staff members [38]. Part of the reason for the respondent’s request appeared to the EJ to be outside the matters that could be taken into account in deciding whether or not there was objective justification [35]. The extra cost and time that would be involved from granting permission for expert evidence would adversely affect the interests of justice [47].

[8]The respondent appealed the tribunal’s First Expert Evidence Decision to this tribunal and in a judgment dated 27 February 2025 HHJ Tayler allowed the appeal (Tesco Stores Limited v Ms K Element & Ors

[2025] EAT 26

). The central criticism of the First Expert Evidence Decision by the EAT was that although the tribunal had ostensibly set out the correct approach to the question of whether to allow expert evidence in accordance with the ET Rules, CPR 35 and the case law of British Airways PLC v Spencer

[2015] EWHC 2477 (Ch)

, the tribunal had failed to apply the law and instead applied a test of whether the issues relied on by the respondent were relevant to the determination of the dispute. HHJ Tayler also noted that the respondent had not identified a proposed economist, stated what particular economic expertise the expert might have beyond being “an economist” nor stated the likely cost.

[9]The respondent agreed to HHJ Tayler deciding the matter for himself, but the claimants’ position was that he should only do so if the only possible decision was that the expert evidence was necessary or was not necessary and in the absence of their agreement the Judge concluded that the issue must be remitted back to the first instance tribunal. The parties also disagreed as to whether the case should be remitted back to the same, or a fresh, tribunal. HHJ Tayler decided to remit it back to the same tribunal, EJ Hyams, rejecting the respondent’s application to remit the matter back to a fresh tribunal. Whilst the EAT noted that the errors were unfortunate and serious, the impugned judgment fell short of being totally flawed. HHJ Tayler considered the principles set out in Sinclair Roche & Temperley v Heard

[2004] IRLR763

and found: “I also consider it has to be seen in the context of the enormous burden of judging such litigation when large legal teams produce vast amounts of material. While the judge lost sight of the correct test to be applied in determining whether to admit expert evidence I consider that he can be trusted now to focus on the correct test and to apply it properly without attempting a second bite of the cherry. I have confidence in his professionalism and that on an application of the correct test and consideration of all the relevant factors he will allow the application if he concludes that is the correct decision or refuse it if that is the correct decision. I have sought to avoid giving any idea of what I might have decided had the parties agreed that I retake the decision and nothing in this judgement should be seen as giving a steer.” [56]

[10]The matter was duly remitted back to EJ Hyams and a further hearing took place on 18 March 2025 at which both parties provided further oral and written submissions. The tribunal described its task as to re-determine the respondent’s application completely afresh. In a judgment sent to the parties on 21 March 2025 (“the Second Expert Evidence Decision”) it found that the respondent, and the claimants if desired, be given permission to adduce expert evidence from an economist on both the Markets Issue and the Consequences Issue, in wording that had been taken directly from the respondent’s skeleton argument before the EAT as follows:

“1. Markets 1.1 Whether the labour markets for the respondent’s stores (“the Stores”) and distribution centres (“DCs”) were different markets/two different segments of the same market; 1.2 whether the relevant labour markets were broader than the respondent’s product market, namely the grocery retail sector; 1.3 whether the respondent’s provisional proposed definitions of the labour markets for Stores and DCs, as set out in its letter of 21 October 2024, are accurate. 1.4 the relevant market rates in the labour markets for Stores and DCs. 1.5 whether the relevant market rate range was different, and specifically whether it was higher, for DCs than for Stores; 1.6 whether the relevant labour markets for DCs and Stores were competitive; and 1.7 whether the market rates were set or at least influenced by the respondent and others sharing market information and whether the respondent had created or contributed to the market forces and their perpetuation, including by collusion with competitors when setting pay rates. 2. Consequences of paying more to the claimants during the relevant period 2.1 How competitors would have been likely to act in response to the respondent being placed at a competitive disadvantage and/or being unable to operate effectively as a result of increasing pay in Stores; 2.2 how customers would have been likely to react to various hypothetical changes in the prices [and competitive offer, assuming that those words add anything material]; and 2.3 how investors and creditors would have been likely to react to various hypothetical levels of reduced dividends or reported profitability and growth.”

[11]The case was then listed for a further half-day hearing on 26 March 2025 to decide the precise form of the orders to be made which were then set out in a decision sent to the parties on 27 March 2025 entitled “Record of a Preliminary Hearing” (“the Third Expert Evidence Decision”) in which the final form of the questions to be addressed by the economists was framed as follows:

“A. Markets 1.1 The relevant market rates in the labour markets for the respondent’s stores (“Stores”) and distribution centres (“DCs”); and 1.2 Whether the relevant labour markets for DCs and Stores were competitive which will involve consideration of whether the market rates were driven by supply and demand factors and whether the Respondent had the market power to set or influence market rates of pay. B. Consequences 1.3 How competitors would have been likely to act in response to the respondent being placed at a competitive disadvantage and/or being unable to operate effectively as a result of increasing pay in Stores; 1.4 How customers would have been likely to react to various hypothetical changes in the prices and competitive offer; and 1.5 How investors and creditors would have been likely to react to various hypothetical levels of reduced dividends or reported profitability and growth.”

[12]The judgments being appealed before me are both the Second and Third Expert Evidence Decisions. There were also two emails from EJ Hyams sent to the parties on 25 March 2025 in response to questions from both Harcus and Leigh Day respectively after receipt of the Second Expert Evidence Decision which are said to be indicative of the EJ’s reasoning, although not said to be decisions under the ET Rules capable of appeal. Second Expert Evidence Decision

[13]In the reasons for the order made in the Second Expert Evidence Decision the tribunal stated that it had concluded that the expert evidence sought by the respondent was “reasonably required to resolve the proceedings” in accordance with r.10(1) Employment Tribunal (Equal Value) Rules of Procedure 2024 (“EV Rules 2024”). Under the heading “My conclusions and brief reasons for them”, the EJ said this about evidence on the Markets Issue:

“5 Mr Coghlin’s [counsel for the respondent] oral submissions in particular persuaded me that there were issues arising in relation to what the respondent called the “markets issue” in relation to which expert evidence from an economist would go beyond the scope of the evidence which a witness of fact could give. That was evidence relating to the issues stated in paragraph 6 of the skeleton argument put before HHJ Tayler by the respondent, which was at SB208-SB209, i.e. pages 208-209 of the supplementary bundle of documents put before me for the purposes of the hearing of 18 March 2025. 6 That was not precisely what the respondent had asked for in its letter stating its application for permission to adduce expert evidence. That letter was dated 29 November 2024 and was at HB122-130, i.e. pages 122-130 of the bundle of documents put before me for both the hearing of 9 December 2024 and the hearing of 18 March 2025. That for which the respondent had asked was stated (shortly and briefly) in paragraph 13 at HB125. 7 It appeared to me that the respondent had in preparing its appeal to the EAT stated more helpfully and with more precision the reasons why it was seeking to adduce expert evidence in relation to the markets issue. To that extent, I disagreed with what Mr Bryant said, as recorded on page 74 of the transcript of the hearing of 18 March 2025, to the effect that the respondent’s application for permission to adduce expert evidence and its pleaded case were without “any degree of clarity”.”

[14]Similarly on the Consequences Issue the tribunal found that the evidence required was more clearly discernible from the arguments that had been put in the EAT than had been before the tribunal initially and on the basis of the reformulation the tribunal now concluded that at least some of the expert evidence sought was reasonably required to resolve the proceedings:

“8 The evidence required on what the respondent called the “consequences issue” was much more clearly discernible from what was said in paragraph 26.3(c)(iii) of the skeleton argument which the respondent put before HHJ Tayler, at SB220-SB221, than from what was said in paragraph 22 of the letter of 19 November 2024 at HB127. I accepted that expert evidence from an economist on those things which were stated in paragraph 26.3(c)(iii) at SB220-SB221 was reasonably required to resolve the proceedings. 9 Similarly to what I say in paragraphs 6 and 7 above, I could see that the formulation in paragraph 26.3.(c)(iii) was not before me on 9 December 2024, and that it appeared to have come into existence only in preparation for the EAT hearing of 14 February 2025. Be that as it may, when reading that formulation I was able to see (1) why the proposed expert evidence stated in it would go beyond the evidence which any witness of fact for the respondent could give and, (2) having re-read and thought again about the approach taken by Roth J in Phones 4U Ltd v EE Ltd [2021] EWHC 2879 (Ch), which was at AB469-AB485 (i.e. pages 469-485 of the authorities bundle), why I should conclude that at least some expert evidence about the things referred to by the respondent as “the consequences issue” was reasonably required to resolve the proceedings. 10 I record, however, that, if only as a matter of logic, the question whether one or more competitors would also have decided (or been obliged) to increase the pay of its stores staff because of a risk of a finding, or a finding, that the work was of equal value to that done by its DC staff, is likely to be an important part of the analysis which will have to be undertaken in relation to the consequences issue. ”

[15]However, there was a caveat that the tribunal would need to hear further from the parties on the precise form of the orders to be made and the list of questions was couched as a provisional view “at this stage” [11]. The decision then set out what were described as some observations and responses to the claimants’ submissions in opposition to the respondent’s application. “15 Asking myself the questions set out in paragraph 18.7 of the judgment of HHJ Tayler in this case, I came to the following conclusions (i.e. I state this for the avoidance of doubt, having come to the conclusions stated in paragraphs 5 and 8 above simply by applying the words of rule 10(1) of what I will call the Equal Value Rules 2024).15.1 The expert evidence of the sort which I have identified in paragraphs 5 and 8 above was necessary for the respondent to prove at least aspects of its case here. Technically, the evidence was not necessary for the case to be resolved, because without it, the respondent would simply have had much difficulty in proving those aspects of its case, and therefore it might not have been able to pursue it successfully in so far as the expert evidence related to it.

15.2 If that were not so, then I would have concluded without any doubt that the evidence was reasonably required because without it the respondent would be likely to have great difficulty in relying on several aspects of its material factor defence, and that defence was potentially dispositive of the proceedings. In addition, and in any event, I accepted the points made in paragraphs 52 and 53 of the respondent’s skeleton argument for the hearing of 18 March 2025.”

[16]The paragraph in HHJ Tayler’s judgment that he refers to is as follows:

“18.7. In British Airways Plc v Spencer & Ors [2015] EWHC 2477 (Ch), [2015] Pens. L.R. 51 Warren J held that in determining whether expert evidence is reasonably required to resolve the proceedings the court must ask itself the following questions: (a) The first question is whether, looking at each issue, it is necessary for there to be expert evidence before that issue can be resolved. If it is necessary, rather than merely helpful, it seems to me that it must be admitted. (b) If the evidence is not necessary, the second question is whether it would be of assistance to the court in resolving that issue. If it would be of assistance, but not necessary, then the court would be able to determine the issue without it (just as in Mitchell the court would have been able to resolve even the central issue without the expert evidence). (c) Since, under the scenario in (b) above, the court will be able to resolve the issue without the evidence, the third question is whether, in the context of the proceedings as a whole, expert evidence on that issue is reasonably required to resolve the proceedings. In that case, the sort of questions I have identified in paragraph 63 above will fall to be taken into account. In addition, in the present case, there is the complication that a particular piece of expert evidence may go to more than one pleaded issue, or evidence necessary for one issue may need only slight expansion to cover another issue where it would be of assistance but not necessary. [emphasis added]” (a) The first question is whether, looking at each issue, it is necessary for there to be expert evidence before that issue can be resolved. If it is necessary, rather than merely helpful, it seems to me that it must be admitted. (b) If the evidence is not necessary, the second question is whether it would be of assistance to the court in resolving that issue. If it would be of assistance, but not necessary, then the court would be able to determine the issue without it (just as in Mitchell the court would have been able to resolve even the central issue without the expert evidence). (c) Since, under the scenario in (b) above, the court will be able to resolve the issue without the evidence, the third question is whether, in the context of the proceedings as a whole, expert evidence on that issue is reasonably required to resolve the proceedings. In that case, the sort of questions I have identified in paragraph 63 above will fall to be taken into account. In addition, in the present case, there is the complication that a particular piece of expert evidence may go to more than one pleaded issue, or evidence necessary for one issue may need only slight expansion to cover another issue where it would be of assistance but not necessary. [emphasis added]”

[17]The EJ observed that when he re-read the respondent’s application for permission to rely on expert evidence, he found himself: “…again being unpersuaded that there was a need for expert evidence of the sort sought in that letter. It was only by reading paragraph 6 of the skeleton argument put by the respondent before HHJ Tayler, at SB208-SB209, and paragraph 26.3(c)(iii) of that skeleton argument, at SB220-SB221, that I was able to see why the respondent was seeking expert evidence from an economist and why it was reasonably required to resolve the proceedings. I noted that in paragraph 6 of that skeleton argument, cross-reference was made to the bases of the elements stated in the paragraph, and that they were diverse and included not just the respondent’s MFD Particulars but also a letter sent by the respondent on 21 October 2024.” [17]

[18]He agreed with the claimants’ submission that “the respondent’s application had evolved over time, and in particular during the course of the appeal of the respondent to the EAT”, but “concluded that that factor did not justify refusing the respondent’s application” [35], since he had concluded that expert evidence on the matters sought was both necessary and reasonably required to determine the proceedings. He accepted the argument that expert economist evidence was also reasonably required for the Consequences Issues, relying on Phones4U Ltd v EE Ltd

[2021] EWHC 2879 (Ch)

and noted that in the ET case of Thandi & Ors v Next Retail Ltd and Next Distribution Ltd (1302019/18) the parties had all agreed that both sides should be allowed to rely on expert economist evidence on similar issues. He drew on the overriding objective in rule 3 of the Employment Tribunal Rules of Procedure 2024.

[19]The EJ accepted: “that in some respects, what the respondent was asserting in paragraphs 25-30 of its MFD Particulars was so obvious (not “self-evident”, but obvious) to the industrial jury in the form of an employment tribunal, the members of which are able to draw on their own day-to-day experiences, that it would not need to be fortified by expert evidence” but he nonetheless concluded that it would “not preclude an expert from referring to the circumstances referred to in those paragraphs, but it would mean that expert evidence on the subject-matter of those paragraphs was not reasonably required for the resolution of the proceedings.” [27]

[20]The EJ said this about Ms Criddle’s criticism that the matters on which expert evidence was sought were not anchored in the pleadings:

“29 Ms Criddle pointed out (as recorded on pages 137 and 138 of the transcript of the hearing of 18 March 2025) that the respondent had, only on 12 March 2025, referred to the concept of “market power” by saying that an economist could give evidence on the question whether the respondent had market power within the claimed labour markets. She then said this. ‘Now, Mr Blake, who knows this litigation inside out, says to me, “Market powers never featured before”, the words “market power” have never featured before in the correspondence and certainly not in the pleadings, and it’s quite a precise competition law concept which is creeping in after this application has originally been heard and very shortly before it’s now being heard again. And this constant drift, this constant lack of clarity, is a matter of significant concern to the claimants.’ 30 It is the Leigh Day claimants’ express position (in paragraph 24.1 of its reply, at HB94) that the respondent has “influenced” the labour market in which it operates. As far as I can see at present, whether it has done so could be assessed properly only if there were expert evidence from an economist on the point: it is unlikely that the respondent could, by calling a witness of fact, show that it had not influenced the labour market in which it operates. However, it may be the case that the acts of an employer as large as the respondent could not avoid influencing the labour market in which it operates. That too, though, could be assessed by the tribunal properly only if it had some expert evidence from (in this instance it appears it would be) an economist on the question. 31 The respondent says that such evidence will be necessary in any event to support its contention (in paragraph 8 of its MFD Particulars, at HB9) that the rates of pay which it set were set by reference to “market conditions”, and it is the claimants’ position that the respondent must prove that they were so set. The claimants say that that question is one of simple fact, and that no expert evidence is either necessary or of assistance in that regard. However, the respondent’s perception of market conditions is one thing, and what those conditions are is another. The respondent can by giving factual evidence prove the first of those things, but not the second. The second thing is something the proof of which would require some expert evidence. Whether such evidence is reasonably required for the resolution of the proceedings is a different question. Ms Criddle said (as recorded at lines 2-5 on page 151 of the transcript) that “What this respondent says is: we paid by reference to what we knew the market to be and the market rate that prevails in that market.”

That, if taken in isolation, might be seen as an acceptance that the respondent’s case required proof of what the market rate was, and that, it seemed to me on the re-hearing of the respondent’s application, was capable of proof only by an independent expert. Ms Criddle continued, at lines 5- 9:

“They’re not saying: well, we don’t know what the market was, but we have had a look at it now, and fortuitously, we find out that we have actually been paying in accordance with the market all along. That’s not this case.” 32 That was true, but it did not detract from the fact that the respondent’s case is, and is seen by the claimants to be, that it paid its staff by reference to the market rates applicable to the staff of its stores and its DCs. 33 In all of the circumstances, I arrived at the firm view that (assuming that reliance on market forces was a proportionate means of achieving a legitimate aim, which I had to assume for present purposes) expert evidence from an economist at least to show what those market rates were, was reasonably required for the resolution of the proceedings. 34 As for the consequences issue, I agreed with the respondent that the respondent’s witnesses of fact could not give credible evidence about how the third parties referred to in paragraph 26(3)(c)(iii) at SB220-SB221 would have reacted to the respondent paying more to its stores staff. The words in that paragraph “for example” were unhelpful in this context. If the respondent wishes to adduce expert evidence about the likely responses of any other persons, then it must say who they are. 35 While I agreed with Mr Bryant and Ms Criddle that the respondent’s application had evolved over time, and in particular during the course of the appeal of the respondent to the EAT against my now-overturned decision to refuse permission to adduce expert evidence from an economist, for the reasons given in paragraph 16 above, I concluded that that factor did not justify refusing the respondent’s application. ” ‘Now, Mr Blake, who knows this litigation inside out, says to me, “Market powers never featured before”, the words “market power” have never featured before in the correspondence and certainly not in the pleadings, and it’s quite a precise competition law concept which is creeping in after this application has originally been heard and very shortly before it’s now being heard again. And this constant drift, this constant lack of clarity, is a matter of significant concern to the claimants.’ “They’re not saying: well, we don’t know what the market was, but we have had a look at it now, and fortuitously, we find out that we have actually been paying in accordance with the market all along. That’s not this case.”

[21]Following its promulgation, the Harcus claimants corresponded directly with the EJ to ask for clarification of a number of aspects of the Second Expert Evidence Decision. They sought clarification of the meaning of “competitive” as used in question 1.6 of the orders made; clarification by reference to the MFD Particulars of the issues on which the experts had been permitted to opine; and for clarification of 13 aspects of the assumed (or hypothesised) scenarios in the Consequences Issue orders. Leigh Day supported Harcus’ letter and raised a number of issues of their own concerning the Second Expert Evidence Decision. They were confused about what had been granted and the reason for granting permission in light of the observation that the “application…might have succeeded if it had been framed differently” [3], when the EJ had then gone on to grant permission. Leigh Day’s question was:

“We therefore seek clarification as to whether the Tribunal by its Second Decision intended to reject Tesco’s application for expert evidence. If so, is the Second Decision to be understood as the Tribunal granting permission for a hypothetical application that might have been (but was not) framed different by Tesco?”

[22]They also had a number of specific concerns on questions 1.1, 1.4 and 1.5 about how the prevailing market rates and differences for the market rates referred to in those questions differed from the factual questions on which the respondent considers itself to be well-informed (as per the MFD Particulars see e.g. [67]). On proposed question 1.2 their concern was that the respondent had not pleaded its market definitions, it had only provided provisional definitions in correspondence. On proposed questions 2.1-2.3, Leigh Day’s concern was that they would not be able properly to instruct an expert when that expert was required to consider the response of third parties to the actions of the respondent which the respondent had not particularised in any way. Leigh Day also noted the inevitability of the autumn 2025 MFD hearing being delayed if the respondent’s application was granted and that there had been no explanation for the respondent’s eight month delay from March (when the 21 March 2024 PH decision was made) to the respondent’s application to the tribunal on 29 November 2024 for permission to adduce expert evidence.

[23]EJ Hyams diligently and mildly responded at speed to both letters (at 8:41am and 9:33am on the day before the 26 March 2025 hearing) giving his thoughts but also stating that they were all matters for debate the next day. In response to the Leigh Day letter he stated that he thought he had been clear that he had:

“….not granted the respondent’s application to adduce expert evidence in the form in which it was made, but that I have concluded that some expert evidence from an economist would fall within the test stated in rule 10(1) EV Rules.”

[24]On the Harcus concern about the meaning of “competitive” he said:

“I was myself doubtful whether it was apt, but I can see at this stage, subject to submissions, that it may have a relevant meaning to an economist.”

[25]He explained that there was no need to be more specific about assumptions to be made in a hypothetical situation “because there will be a range of them, and the issue of what the respondent would have done in a number of scenarios may be a matter of factual assertion rather than assumption at this stage.” Third Expert Evidence Decision

[26]In the Third Expert Evidence Decision after the 26 March hearing the tribunal recorded how the respondent had now defined the labour markets or labour market segments for their stores and DC staff in a letter of 21 October 2024:

“5.1 ‘The labour market from which the Respondent hired its Store workers at the relevant time was a national market comprising a geographically well- distributed, overlapping “patchwork” of jobs and labour made up of a subset of the unskilled labour market, with workers in this market generally looking for or generally working in jobs such as retail, hospitality, and customer service (the Stores Labour Market).’ 5.2 ‘The labour market from which the Respondent hired its DC workers at the relevant time was comprised of a series of separate local markets generally located near distribution and logistics hubs in areas easily accessible to major motorways, with each local market comprising a subset of the local unskilled labour market, with workers in each local market generally looking for or generally working in jobs such as warehousing, manufacturing, distribution and logistics (each a DC Labour Market).’ ”

[27]The precise form of wording of the questions to be addressed by the experts was discussed. The tribunal was told who the respondent proposed to instruct, a Professor Card. His identity was revealed to the claimants shortly before the hearing that resulted in the Second Expert Evidence Decision. He is an Emeritus professor of the University of California, Berkeley and was awarded the Nobel Memorial Prize in Economics in 2021 and has been awarded a host of other awards and prizes since 1978 mainly in the United States of America. He was the Director of Labor Studies Programme for the National (US) Bureau of Economic Research from 2008-2017 and the founding director of the Center for Labor Economics, UC Berkeley 1997-2022. It was not evident from his CV if he had specialist expertise in the UK labour market. The respondent informed the EJ and claimants of the cost of expert evidence orally at the hearing on 18 March 2025. During the course of the hearing before me I was told his fee was £850,000. I was not told if that was for an initial report or would cover all anticipated work.

[28]The tribunal gave the claimants (collectively) and the respondent permission to each call either one or two experts to deal with both the Markets and the Consequences Issues, with the usual directions concerning service, joint meetings and permission to call all experts to give oral evidence at the hearing that had then been listed for 2 months from 1 September to 24 October 2025, which has since been postponed at the joint request of the parties to Spring 2026 with the same time estimate. Statement of case: MFD Particulars and claimants’ replies

[29]It is necessary to set out how the respondent puts its case on MFD and how the claimants responded. The respondent has relied on material factors relating to labour markets and the consequences for its competitiveness it is asserted would arise from pay equalisation from the outset. In the ET3 responses to the claims in February 2020 four MFDs were advanced in general terms:

“28. Further or alternatively, any differences in pay or other terms (if any) relied upon by the claimants have not resulted from any sex discrimination or from any sex discrimination by the respondent or for which it is legally responsible but has or may have resulted from other material factors (whether demographic, sociological, economic, historical or otherwise, and as to which the respondent reserves the right to adduce evidence) including but not limited to: i. Differences in the arrangements for determining pay as between stores and DCs, including different collective bargaining agreements and the fact that the dates on which these were implemented vary; ii. Differences in the conditions of supply and demand in the relevant markets for labour, iii. Differences in the market price of the various types of labour in the relevant markets, and iv. The need for the respondent to keep its retail and its distribution labour costs within efficient levels, for the purposes of recruitment and retention and to enable it to compete effectively in the markets in which it operates and has from time to time operated.”

[30]It then provided a nine page letter containing what it described as a non-exhaustive list of MFDs that it asserted operated at a collective level across its distribution centre network. The respondent was ordered to provide details of its MFD with details of the time, the factor applied and, if the factor has ceased to apply, the date it ceased to apply by EJ Manley on 11 November 2021 (before her retirement when EJ Hyams became the assigned EJ allocated to these cases). The respondent then provided a further seven-page letter on 4 March 2022 which it again described as a non-exhaustive list of MFDs that operated at an individual level in relation to the comparators from 18 February 2012 to 31 August 2018. At the hearing resulting in the 21 March 2024 PH EJ Hyams gave the respondent permission to add to its pleaded case on MFDs by 31 May 2024 to set out any MFD and if it sought to justify the material factor, setting out the particulars on which it relies to show that the material factor was a proportionate means of achieving a legitimate aim. The MFD Particulars document was served on 7 June 2024 and runs to 64 pages (“the MFD Particulars”). That is now the only document that forms part of the respondent’s statement of case on MFDs.

[31]Nine material factors are relied on by the respondent in the MFD Particulars: i) MFD 1: Recruitment and retention; ii) MFD 2: Competition, stability, sustainability and performance; iii) MFD 3: Different methods of determining pay and different packages of terms; iv) MFD 4: Avoiding disruption to the respondent’s distribution network; workplace stability and good industrial relations; v) MFD 5: TUPE; vi) MFD 6: Productivity; vii) MFD 7: Attendance; viii) MFD 8: Encouraging working at night, weekends and bank holidays; and ix) MFD 9: Flexibility and common terms.

[32]MFDs 1 and 2 are relevant to the Markets Issue and the Consequences Issue about which the MFD Particulars said this:

“66. A key factor in agreeing terms in relation to pay in both DCs and Stores was the prevailing rates of pay in the relevant competitive labour market segments from which the DCs and Stores drew their workforces.” 67. The Respondent’s Stores and DCs compete for labour in different segments of a competitive labour market…These different segments of the labour market have different supply and demand characteristics, which result in different market prices. The Respondent, and the unions with which it negotiates to agree the pay of colleagues both in Stores and DCs, are experiences and are well informed as to the prevailing market rates 68. The Respondent’s core aim - which is to run a sustainable and profitable business for the benefit of its stakeholders – requires it to pay its distinct workforces, in DCs and in Stores, in accordance with the prevailing rates in the distinct segments of the labour markets from which it recruits those workforces. MFDs 1 and 2 represent the two sides of this coin. 69. It is necessary to pay in line with the market price for labour in order to secure a sufficient number of colleagues of sufficient quality, and to retain those colleagues. This is necessary to ensure the continuation, efficiency and resilience of the Respondent’s operations. Paying less than the market rate would be strongly resisted by the unions representing those colleagues (whose negotiating power would be increased by the Respondent’s difficulty in recruiting new colleagues if it was paying below market rates). 70. Market prices for hiring into relevant Store roles have at all material times been lower than those for hiring into relevant DC roles. As with any jobs, the market price is a range, with businesses adopting rates within that range that are sufficient to attract enough workers of an appropriate standard to meet the requirements of that business. 71. By paying in line with market rates, the Respondent was consistently able to recruit and retain a sufficient number of suitable Customer Assistant colleagues in its Stores. 72. For DCs, the Respondent needed to pay the (higher) market rate in order to recruit and retain a sufficient number of suitable workers to fill its warehouse operative roles. These roles are harder to recruit for, and to retain colleagues in, than roles in Stores, and market rates are higher in this labour market segment. This is due to a complex of reasons which change over time but which consistently included the location of DCs, the working environment (including continuous monitoring), and the nature of the warehouse operative role.”

[33]The respondent relied on 17 legitimate aims in support of each of its MFDs, nine of which were said to be relevant to MFDs 1 and 2. They are: i) LA 1: operating effectively as a sustainable, stable and profitable business; ii) LA 2: Recruiting and retaining a sufficient number of suitable colleagues to meet its operational requirements; iii) LA 3: Competing effectively, and not placing itself at a competitive disadvantage; iv) LA 4: Controlling wage bill costs where the rationale for paying higher wages which existed in DCs did not apply in Stores; v) LA 5: Ensuring the continuation and resilience of the Respondent’s distribution network both generally and at peak periods of demand; vi) LA 7: Protecting the Respondent, its colleagues and its customers from the consequences of failures or other disruption to its distribution network; vii) LA 10: Maintaining 24/7 work within its DCs throughout the year; viii) LA 11: Incentivising and achieving consistent and high attendance within the DCs, particularly during times of high demand (such as Christmas); ix) LA 12: Incentivising colleagues at DCs to work on particular days and at particular times, including overtime hours, unsociable hours, at night, at weekends and on Bank Holidays so as to ensure that the Respondent’s operational needs are met.

[34]In response to the MFD Particulars both sets of claimant solicitors each served a reply. These too were lengthy documents. Neither gave any quarter; the respondent was put to strict proof on every matter pleaded.

[35]The Harcus claimants’ reply to the MFD Particulars, served on 5 July 2024, illustrates the scale of the dispute between the parties on the MFD. By way of background, the parties had previously been required to identify the pay and contractual terms applicable to the claimants and the comparators in an Identification of Terms Schedule, which was understandably complex given the size of the workforce and the pay arrangements – different arrangements for matters such as premium pay, attendance, overtime, holiday and sick pay, productivity bonuses as well as basic hourly rates. The Harcus claimants’ response stated that the Identification of Terms Schedule remained in dispute in all respects.

[36]The parties seem also not to be agreed as to whether the claimants are entitled to rely on a term by term comparison of each element of their pay with their comparators or an overall package basis. The Harcus claimants’ position is that none of the MFDs advanced are said to be material, nor were any of them accepted to genuinely explain the differences between the relevant terms. The market forces MFD was said to be tainted by sex (s.69(1)(a) EqA 2010); and/or there was indirect discrimination (particular disadvantage in the language of s.69(2)) from the ‘sex-skew’ of the workforce that the respondent could not objectively justify.

[37]The parties appear to be in dispute as to whether the MFD Particulars applied to just the sample claimants or the wider cohort of all tranche 1 claimants. There was also criticism in the Harcus claimants’ reply of a vagueness and lack of detail in the MFD Particulars, notwithstanding their length. For example for MFDs 1 and 2 the Harcus claimants said that there was no proper explanation of terms such as: ‘segments’ of a ‘labour market’, ‘different supply and demand characteristics’, ‘different market prices’, ‘prevailing rates of pay in this labour market’, ‘prevailing rates in the distinct segments of the labour markets’ , nor the basis on which they were said to explain the relevant terms or differences [24].

[38]The Leigh Day claimants also provided a full response (29 pages) which made similar points to the Harcus claimants. They gave more emphasis to the criticism of the lack of transparency of the 9 MFDs and 17 legitimate aims put forward by the respondent which, despite the apparent complexity of the MFD Particulars, amounted to the single core argument of the “market” which, crucially, it had not identified. Other criticisms (if the respondent could prove the factual assertions all of which were disputed, just as they were by the Harcus claimants) were that there had been no identification of the process for decision-making in relation to pay (and in particular which employees and directors were responsible for making those decisions and the reasons for them). The respondent had not shown or attempted to show that the markets were not discriminatory and nor had they shown (or attempted to show) that the unions were not influenced in their approach to negotiations by sex.

[39]Leigh Day also asserted that the respondent has the ability to influence market rates for claimants and comparators by its size. It has also shared information with competitors which has created or contributed to relevant pay rates (paragraphs 24.1 and 42.1 in its reply).

[40]The Leigh Day claimants provided detailed examples of the ways in which it considered that the MFD Particulars were deficient and lacked transparency.

[41]Both sets of claimants were also strongly critical of the respondent’s attempt in the MFD Particulars to try to reserve the right to make further amendments.

[42]In correspondence about expert evidence the claimants repeatedly stated that the proposals were so vague that it was not possible to understand the specific issues upon which the respondent was proposing to adduce expert evidence (see Harcus’ second letter dated 25 September 2024 for example). There were repeated requests for clarity. The respondent solicitors did provide some useful commentary and explanation in some of the many letters passing between the parties, but the few nuggets are somewhat buried in the verbiage and do not have the status of pleadings.

[43]The Leigh Day claimants provided a response to the respondent’s request for further particulars of their reply on 14 October 2024 which set out in greater detail its allegation that the different pay bargaining arrangements were tainted by direct and indirect discrimination and the role of the union USDAW and sought disclosure from the respondent on union acquiescence in discriminatory pay. The grounds of appeal

[44]All five grounds of appeal were given permission to proceed to a full hearing following a paper sift under Rule 3(7) EAT rules of procedure by HHJ Tayler, but it is accepted that Ground 3 (that expert evidence was being allowed that might be uncontested because the claimants did not have sufficient time to call evidence of their own) is now academic, since the parties have now agreed to delay the MFD hearing till 2026 to enable both sides to have sufficient time to prepare, whatever the outcome of this appeal. The four remaining grounds are all aspects of the central criticisms that the tribunal failed to anchor the expert evidence to the respondent’s pleaded case and a failure to identify the issues on which the expert evidence would be required, described by Ms Criddle as a wholesale failure, in that it: i) Failed to apply the Spencer guidance by failing to identify the pleaded issues for which expert evidence was either necessary or reasonably required; indeed, the tribunal said repeatedly in the course of the hearing that expert evidence should not be tied to the respondent’s pleaded case; ii) Allowed expert evidence on a “provisional basis” in the abstract without identifying the questions based on the pleaded issues which the expert would be required to address; iii) Allowed expert evidence on the Markets Issue without identifying the pleaded issues to which that evidence related or how such evidence could assist the ET in its determination of the respondent’s MFDs; and iv) Allowed expert evidence on the Consequences Issue in the absence of any properly pleaded case from the respondent and despite stating in terms that it did not understand the issues on which the expert was to be asked to opine.

[45]These were said to amount to errors of law that fell outside the tribunal’s wide discretion and powers in matters of case management. The challenge was twofold – that permission to adduce expert evidence was granted on matters that were not pleaded issues in some respects, and on matters that were so unclear as to be opaque to the point of meaninglessness.

[46]The Second Expert Evidence Decision was also criticised as being internally inconsistent, and failing to provide adequate reasons for its conclusions.

[47]It was agreed at the outset of the hearing that there would be insufficient time for issues of disposal to be addressed so that in the event of any part of the appeal succeeding, the parties may have a further opportunity to make representations. The law

[48]The relevant law applicable to applications to adduce expert evidence by a first instance court or tribunal is uncontroversial and is not in dispute and was helpfully set out by HHJ Tayler in his judgment at paragraphs [18.1- 18.10] and I gratefully adopt his summary:

“18.1. There are no specific provisions in the ET Rules that apply to determining an application to adduce expert evidence. 18.2. However, the Equal Value Rules provide the statutory test that was applicable in this application: (1) The Tribunal must restrict expert evidence to that which it considers is reasonably required to resolve the proceedings. 18.3. An application to adduce expert evidence should be determined in accordance with the overriding objective. 18.4. The Employment Tribunal may be assisted by consideration of the provisions of the CPR that deal with expert evidence (having regard to the different nature of proceedings in the Employment Tribunal and the Courts, including the costs regime): De Keyser Ltd v Wilson [2001] IRLR 324 (at paragraph 36) and Morgan v Abertawe Bro Morgannwyg University [2020] ICR 1043 (at paragraph 19) . 18.5. The overarching principle (which Rule 10 of the Equal Value Rules adopts) is set out in CPR 35.1 : 35.1 Duty to restrict expert evidence Expert evidence shall be restricted to that which is reasonably required to resolve the proceedings. [emphasis added] 18.6. The CPR further provides: 35.4— Court's power to restrict expert evidence (1) No party may call an expert or put in evidence an expert's report without the court's permission. (2) When parties apply for permission, they must provide an estimate of the costs of the proposed expert evidence and identify — (a) the field in which expert evidence is required and the issues which the expert evidence will address; and (b) where practicable, the name of the proposed expert. (3) If permission is granted it shall be in relation only to the expert named or the field identified under paragraph (2). The order granting permission may specify the issues which the expert evidence should address [emphasis added] 18.7. In British Airways Plc v Spencer & Ors [2015] EWHC 2477 (Ch), [2015] Pens. L.R. 51 Warren J held that in determining whether expert evidence is reasonably required to resolve the proceedings the court must ask itself the following questions: (a) The first question is whether, looking at each issue, it is necessary for there to be expert evidence before that issue can be resolved. If it is necessary, rather than merely helpful, it seems to me that it must be admitted. (b) If the evidence is not necessary, the second question is whether it would be of assistance to the court in resolving that issue. If it would be of assistance, but not necessary, then the court would be able to determine the issue without it (just as in Mitchell the court would have been able to resolve even the central issue without the expert evidence). (c) Since, under the scenario in (b) above, the court will be able to resolve the issue without the evidence, the third question is whether, in the context of the proceedings as a whole, expert evidence on that issue is reasonably required to resolve the proceedings. In that case, the sort of questions I have identified in paragraph 63 above will fall to be taken into account. In addition, in the present case, there is the complication that a particular piece of expert evidence may go to more than one pleaded issue, or evidence necessary for one issue may need only slight expansion to cover another issue where it would be of assistance but not necessary. [emphasis added] 18.8. If expert evidence would be helpful in determining an issue, but is not necessary, a balancing exercise must be conducted. Warren J referred to some of the potentially relevant factors at paragraph 63 of his judgment: “In striking that balance, the court should, in my judgment, be prepared to take into account disparate factors including the value of the claim, the effect of a judgment either way on the parties, who is to pay for the commissioning of the evidence on each side and the delay, if any, which the production of such evidence would entail (particularly delay which might result in the vacating of a trial date).” 18.9. In JP Morgan Chase v Springwell [2006] EWHC 2755 Aikens J warned against the introduction of expert evidence in commercial disputes merely because they concern "a very large sum of money" or require the consideration of "a huge amount of documents", noting that: “The result is that, all too often, the judge is submerged in expert reports which are long, complicated and which stray far outside the particular issue that may be relevant to the case. Production of such expert reports is expensive, time-consuming and may ultimately be counter-productive. That is precisely why CPR Pt 35.1 exists. In my view it is the duty of parties, particularly those involved in large scale commercial litigation, to ensure that they adhere to both the letter and spirit of that Rule. And it is the duty of the court, even if only for its own protection, to reject firmly all expert evidence that is not reasonably required to resolve the proceedings.” (1) The Tribunal must restrict expert evidence to that which it considers is reasonably required to resolve the proceedings. Expert evidence shall be restricted to that which is reasonably required to resolve the proceedings. [emphasis added] (a) the field in which expert evidence is required and the issues which the expert evidence will address; and (b) where practicable, the name of the proposed expert. (a) The first question is whether, looking at each issue, it is necessary for there to be expert evidence before that issue can be resolved. If it is necessary, rather than merely helpful, it seems to me that it must be admitted. (b) If the evidence is not necessary, the second question is whether it would be of assistance to the court in resolving that issue. If it would be of assistance, but not necessary, then the court would be able to determine the issue without it (just as in Mitchell the court would have been able to resolve even the central issue without the expert evidence). (c) Since, under the scenario in (b) above, the court will be able to resolve the issue without the evidence, the third question is whether, in the context of the proceedings as a whole, expert evidence on that issue is reasonably required to resolve the proceedings. In that case, the sort of questions I have identified in paragraph 63 above will fall to be taken into account. In addition, in the present case, there is the complication that a particular piece of expert evidence may go to more than one pleaded issue, or evidence necessary for one issue may need only slight expansion to cover another issue where it would be of assistance but not necessary. [emphasis added] “In striking that balance, the court should, in my judgment, be prepared to take into account disparate factors including the value of the claim, the effect of a judgment either way on the parties, who is to pay for the commissioning of the evidence on each side and the delay, if any, which the production of such evidence would entail (particularly delay which might result in the vacating of a trial date).” “The result is that, all too often, the judge is submerged in expert reports which are long, complicated and which stray far outside the particular issue that may be relevant to the case. Production of such expert reports is expensive, time-consuming and may ultimately be counter-productive. That is precisely why CPR Pt 35.1 exists. In my view it is the duty of parties, particularly those involved in large scale commercial litigation, to ensure that they adhere to both the letter and spirit of that Rule. And it is the duty of the court, even if only for its own protection, to reject firmly all expert evidence that is not reasonably required to resolve the proceedings.”

[49]The way in which an appellate court or tribunal should consider the matter is also uncontroversial. Case management decisions should not be overturned unless they fall outside the very broad judicial discretion open to the tribunal and are Wednesbury unreasonable (Noorani v Merseyside TEC Ltd

[1999] IRLR 184

). For a perversity challenge to succeed there must be an “…overwhelming case…that the employment tribunal reached a decision which no reasonable tribunal, on a proper appreciation of the evidence and the law, would have reached” Yeboah v Crofton

[2002] IRLR 634

[93] Mummery LJ

[50]Demonstrating the extent of his Thesaurus skills in an earlier case as Mummery J in Stewart v Cleveland Guest (Engineering) Ltd

[1994] IRLR 440

[33] he suggested other iterations of the same principle:

“This [EAT] Tribunal should only interfere with the decision of the Industrial Tribunal where the conclusion of that Tribunal on the evidence before it is ‘irrational’, ‘offends reason’, ‘is certainly wrong’ or is ‘very clearly wrong’ or ‘must be wrong’ or ‘is plainly wrong’ or ‘is not a permissible option’ or ‘is fundamentally wrong’ or ‘is outrageous’ or ‘makes absolutely no sense’ or ‘flies in the face of properly informed logic’.”

[51]Reasons should be read fairly, as a whole and without being hypercritical (DPP Law Ltd v Greenberg

[2021] EWCA Civ 672

) and reasons for case management decisions may be very short and do not necessarily need to address all issues raised (rule 60(6) ET Rules of Procedure). Appellate courts should be slow to interfere in case management decisions and a specialist tribunal such as the Employment Tribunal can generally be assumed to have applied the correct tests, particularly if it has referenced them in its decision, unless the contrary is shown. Kerr J emphasised the need for deference where a case is conducted by an assigned managing judge with prior experience of the case (Tesco Stores Ltd v Element

[2024] EAT 83

[74]).

[52]It is necessary to set out only briefly and in outline the substantive law on MFDs that the tribunal will need to apply at the MFD hearing which is set out in s.69 EqA 2010:

“Defence of material factor (1) The sex equality clause in A's terms has no effect in relation to a difference between A's terms and B's terms if the responsible person shows that the difference is because of a material factor reliance on which— (a) does not involve treating A less favourably because of A's sex than the responsible person treats B, and (b) if the factor is within subsection (2), is a proportionate means of achieving a legitimate aim. (2) A factor is within this subsection if A shows that, as a result of the factor, A and persons of the same sex doing work equal to A's are put at a particular disadvantage when compared with persons of the opposite sex doing work equal to A's. … (6) For the purposes of this section, a factor is not material unless it is a material difference between A's case and B's.”

[53]Thus, the first step, assuming that the work of a claimant and a comparator is equal work, in this case work of equal value, is for the respondent employer to show to the civil standard the genuine reason, or set of reasons, for the difference in pay between the claimant and her comparator. In other words, it is for the employer to show why the pay is different between them – what is it “because of” - in the words of s.69(1), or what is the genuine explanation, or “material factor” (s.69(1)) for the difference in pay? The second step is to consider if the explanation involves less favourable treatment because of sex (direct discrimination). There is some dispute between the parties as to where the burden of proof lies in this step which it is not necessary to resolve for the purposes of this appeal. Once the employer has shown a material factor and it does not involve direct discrimination, it is for the claimant to show a particular gender disadvantage in pay (s. 69(2)) – such as the classic Enderby type form of indirect discrimination for example, or where the gender pattern of pay inequality is the result of historical discrimination based on concepts of men’s work and women’s work, job segregation or part-time work. Where the claimants can satisfy the test in s.69(2), the burden then passes to the respondent to objectively justify the pay differential by proving it is a proportionate means of achieving a legitimate aim, which is the fourth and final step. Analysis and conclusions

[54]The thrust of the respondent’s submission was that there is really nothing to see here: the tribunal had made a perfectly sensible case management decision after having the benefit of EAT guidance which it had expressly referred to and apparently followed, after hearing two days of submissions. The EJ knew all about the case and had had the benefit of three years of being the dedicated assigned managing judge dealing with both case management and substantive decisions following EJ Manley’s retirement. It followed, continued the respondent, that its conclusion which was to grant the respondent’s entirely reasonable request for expert evidence, with no substantive alteration to the orders sought, was very well within the EJ’s wide case management powers. Expert evidence of the type sought was entirely routine,just as it was in the MFD hearing in the ET case of Thandi v Next which also concerned pay differentials between store and DC staff in the retail sector.

[55]Those were powerful and well made arguments. I remind myself that the test is whether the decision is Wednesbury unreasonable and outside the generous ambit where reasonable disagreement is possible (Noorani). No-one is interested in what I might have done had I been the first instance judge, but I must only decide if the decision taken was wrong, as in outside the area of reasonable disagreement.

[56]But in spite of everything so eloquently said by Mr Coghlin, I have grave concerns that the decisions reached cannot stand and have reluctantly concluded that they cannot. The principal reason for this is that the issues have not yet been identified and unless and until the issues have been properly identified it cannot be known what expert evidence is reasonably required to resolve the proceedings. Lack of identification of the issues

[57]As set out in CPR 35.4(2) the parties must identify the issues which the expert evidence will address. The lack of identification of the issues is evident in a number of ways. Ms Criddle pointed to the respondent’s divergence from the pleaded issues in its arguments to the EAT on which the EJ based his decision. She is right to do so. The tribunal does not refer to the pleaded issues in either decision. Instead, in relation to the Markets Issue the tribunal relied on paragraph 6 of the respondent’s EAT skeleton which set out seven alleged issues only three of which are tied to the MFD Particulars. Matters stated at paragraphs 6.3, 6.4 and 6.5 are not.

[58]There was a lack of clarity in the respondent’s definitions of the labour market, which it still described as provisional. Although the tribunal recorded what the respondent had provisionally said it relied on as the “market” for store and DC staff respectively in the Third Expert Evidence Decision, it was silent on whether the respondent was being permitted to retain the provisional label, which was an important omission. It was also troubling that the ET had appeared to have made its Second Expert Evidence Decision without knowing this crucial piece of information.

[59]In relation to the Consequences Issue, the tribunal based its decision on paragraph 26.3(c)(iii) of the respondent’s skeleton before the EAT. There are two difficulties with this. It is not anchored to the issues and is imprecisely worded: “On the Consequences Issue, the Tribunal will need to consider, for example, how competitors would have been likely to act in response to the Respondent being placed at a competitive disadvantage and/or being unable to operate effectively as a result of increasing pay in Stores; how customers would have been likely to have reacted to various hypothetical changes in the prices and competitive offer; and how investors and creditors would have been likely to react to various hypothetical levels of reduced dividends or reported profitability and growth;

[60]Nor does it identify the pleaded issues on which the expert evidence will assist. It also appears that the respondent is seeking to keep matters open ended and to reserve to itself the right to rely on other examples which is problematic.

[61]Another example of lack of clarification of the issues was the fact that the parties were not even agreed whether the MFD hearing would apply only to the sample claimants and comparators or the wider cohort of all tranche 1 claimants.

[62]If the issue relied on does not emerge clearly from an objective analysis of the statements of case it is not an issue in the case (see Moustache v Chelsea and Westminster Hospital NHS Foundation Trust

[2025] IRLR 470

at [38]). If something is not an issue in the case it is unlikely to require expert evidence. Given the unsatisfactory way in which the decisions do not set out or refer to paragraphs in the pleadings it is not possible to unravel how the orders made relate to the pleaded case.

[63]The lack of clarity of the issues is also illustrated by the way in which the application evolved and changed during the course of the litigation from ET to EAT, back again to the ET and then back again before me in this hearing. In the Second and Third Expert Evidence Decisions the EJ did not base his decision on the application for expert evidence set out in the respondent’s letter of 29 November 2024. Instead it was predicated on the respondent’s skeleton argument before the EAT in the challenge to the First Expert Evidence Decision, which went beyond the pleaded issues in the lengthy MFD Particulars and the application itself.

[64]This is evident at various points in the decision. The tribunal explains in the Second Expert Evidence Decision in paragraphs [5–10] that the respondent’s application to adduce expert evidence was different to what it had asked for in the appeal in the EAT ([6]); the formulation in the skeleton argument before the EAT “was not before me on 9 December 2024; and, that it appeared to have come into existence only in preparation for the EAT hearing of 14 February 2025” [9]. The tribunal agreed with Mr Bryant and Ms Criddle “that the respondent’s application had evolved over time, and in particular during the course of the appeal of the respondent to the EAT” [35]. Even after making allowances for an understandable degree of defensiveness on the part of the tribunal in explaining why it had changed its position completely from its First Expert Evidence Decision, the respondent has moved the goal posts during the course of the appeal.

[65]The tribunal’s failure to identify which pleaded issues the expert evidence is required for is also contrary to the express wording of CPR 35.4(2) that had been set out verbatim and highlighted by HHJ Tayler and which the tribunal had been directed to follow. Although the tribunal stated that it had, it does not appear to have done so. The authority of Phones 4U was helpful and one can see in that case the meticulous way that Roth J clearly articulates the issue to which the expert evidence will go, identifies the precise pleading that identifies the issue (including the paragraph number of the APOC) and spells out how the expert evidence might assist with the ultimate question for trial (see paragraphs [1] and [19]-[37]). It contrasts markedly with the approach here. Wording of the questions and imprecision of field of expertise

[66]Even if the issues were clear and even if the issues that would be helped by expert evidence were spelt out, there is a further difficulty in the wording of some of the questions themselves. They lack clarity and precision. Question 1.2 for example (see paragraph 11 above) uses the term “competitive” without any identification of what is meant by the term. Both sets of claimant solicitors had identified the need for the term to be clarified in their letters to the tribunal of 25 March 2025. The term “market power” was also problematic both because it was not a term used in the statements of case and because it was unclear to the claimants’ side what it meant. The decisions did not address the claimants’ argument that the Leigh Day reply (on which the respondent based its application for what became question 1.2) did not identify an issue on the hypothetical concept of market power but raised an issue of fact around how the respondent set its pay rates and shared information with competitors. In the Third Expert Evidence Decision the tribunal admitted that it did not understand the term but “concluded that it was likely to mean something to an economist” [8]. If the tribunal did not understand the term, how could it decide if was a matter on which expert evidence was reasonably required? There are other examples in the decisions and correspondence which indicate that the tribunal has not grasped or understood the issues that will need to be decided at the MFD hearing. There is a conspicuous absence in the EJ’s email of 25 March at 9.33am to the parties when he says that he has concluded that some expert evidence from an economist would fall within r.10(1), but he does not say what evidence or in relation to what issues. The difficulty is that even when that email is read in sequence after the Second Expert Evidence Decision and before the Third Expert Evidence Decision it does not make the position clear nor state with sufficient clarity what issues the expert evidence will address.

[67]The questions on the Consequences Issue which were permitted based on paragraph 26.3(c)(iii) of the respondent’s EAT skeleton on the Consequences Issue leave matters open as to the scope of the evidence permitted to be adduced. Given its speculative nature it begs many questions such as what various hypothetical scenarios or changes in prices, reactions to changes etc? With very basic sequential service of reports, one can see major problems ahead without the parameters of the expert evidence being properly nailed down at this stage. What if the respondent’s expert and the claimants’ expert have different ideas about what scenarios are appropriate, and each prepare reports that cannot easily be compared to each other, using different assumptions and methodologies perhaps, which do not then assist a tribunal with the issues because the basic ground rules have not been established?

[68]Another area of concern is the lack of specificity of the type of economic evidence sought. “Economics” is a very broad field. It is as wide as, for example, medicine. One cannot imagine an order in a clinical negligence or personal injury case giving permission to call “a doctor” or “a medic” without specifying the specialty and the issues to be addressed. Something a little more specific than “economist” is required by CPR 35.4(2) to identify the “field” of the expert. Again there is an interesting comparison with the Phones 4U case where unusually, anti-competitive collusion was being alleged in civil proceedings and not in an investigation and proceedings by a competition authority. But in that case Roth J is very careful to identify with precision the area of economic expertise from an economist and chartered accountant who was also a specialist panel member at the Competition and Markets Authority.

[69]The skeleton argument before the EAT did not provide assistance, referring to merely “the economic issues arising under the Markets Issue or the counterfactual issues arising under the Consequences Issue” (26(d)).

[70]The case of Thandi v Next is only of limited assistance to the respondent since just one of the questions sought by the respondent in this case (question 1.1) is similar to questions that the parties in Thandi agreed should be addressed by expert evidence. The context of the history of the litigation

[71]The respondent’s application also has to be seen in the context of the procedural history of the case. This is a case in which rigorous case management and control of the proceedings is essential. Both sides appear to be conducting a war of attrition, making few, if any concessions whatsoever. It requires the tribunal to be focussed and clear to avoid inadvertently providing opportunities for further disagreement between the parties. There is something of an arms race going on with ever longer documents being produced on both sides and a volume of inter partes correspondence. All this makes it both all the more vital yet difficult for the tribunal to manage the case and keep the necessary control of the proceedings. The parties and the tribunal need to be clear about what the pleaded issues are and to narrow them if possible and only then can it be known what evidence will be required for the tribunal to resolve them.

[72]This case already has a chequered history in making progress which makes rigorous case management and focus on the issues even more important. I note that there have already been eight EAT judgments on preliminary issues and case management decisions in this case since 2021 Tesco Stores Ltd v Element [2021] WLUK 474, Choudhury J in which the respondent unsuccessfully appealed the ET decision to order disclosure of documents and information relating to comparators in the course of equal pay claims. Element v Tesco Stores Ltd

[2022] EAT 165

, Stacey J, Appeal dismissed, the claimants’ challenge to the ET’s decision that preparatory work embarked on around job evaluation was not a “valid Job Evaluation Exercise” for the purposes of the equal work provisions. Abbey v Tesco Stores Ltd

[2024] EAT 76

, Eady J. The claimants’ appeal against disclosure orders and the maintenance of a partial stay of one group of claimants so that the respondent did not need to file ET3s was rejected. Tesco Stores Ltd v Element

[2024] EAT 83

Kerr J order discussed above. Tesco Stores Ltd v Element

[2025] EAT 26

HHJ Tayler – First Expert Evidence Decision, discussed above Tesco Stores Ltd v Element

[2025] EAT 43

HHJ Tayler – scope of grounds of appeal to EAT Stage 2 equal value hearing Tesco Stores Ltd v Element

[2025] EAT 45

HHJ Tayler, preliminary hearing,permission to appeal stage 2 equal value Tesco Stores Ltd v Element

[2025] EAT 112

Stacey J, stage 2 equal value hearings (many of which were combined appeals from different decisions so that the number of ET decisions appealed is well over ten), and there is at least one ongoing appeal to the Court of Appeal which has been listed for February 2026 (on an expedited basis). The appellate history has made me more mindful of the need only to overturn a case management decision if it is essential to do so.

[73]But the other side of that coin is that given the ability of the parties to disagree about every matter possible, it is essential for there to be total clarity about what the expert evidence could specifically address and for the issues to be identified and pinned down so that there can be no misunderstanding.

[74]I also regrettably had to agree with Ms Criddle’s submission that there were parts of both decisions that were hard to follow and internally inconsistent that strayed beyond mere infelicitous wording, but in light of the more substantive problems it is not necessary to dwell on them. I took both sets of claimant legal teams’ emails of 25 March 2025 to express genuine confusion about what had been ordered and the meaning of the Second Expert Evidence Decision, not game playing or positioning on their part. I too had trouble understanding parts of both the Second and Third Expert Evidence Decisions. Conclusion

[75]Until the issues have been properly identified in manageable form and there is clarity over how the respondent says that the expert will assist with resolution of the identified issues, the tribunal will not be able properly to assess the respondent’s application. I have therefore found that allowing the Second and Third Expert Evidence Decisions to stand will result in more confusion and delay further down the line, contrary to the overriding objective, and merely stores up more trouble for later. It will be a recipe for chaos and obfuscation.

[76]Focus must be maintained. In the language of cliches, at the moment the cart is before the horse which means that the cart will have great difficulty in moving in any direction and, if any movement is achieved, who knows in what direction and it will not necessarily be forward.

[77]So I am forced to conclude that both decisions were “wrong” and fell outside the particularly wide case management powers available to an assigned managing judge in complex litigation. That does not mean that no expert evidence may reasonably be required, but before that question can be answered the parties must agree (or have decided for them) what the MFD issues are, to be narrowed if possible, with robust case management, and for the parameters to be clearly understood: no more provisional assertions and both sides to nail their colours to the mast. They must also all be clear on whether the MFD hearing will apply to all tranche 1 claimants or only the sample tranche 1 claimants. In this case, it is the only way that the expert evidence will be manageable given the behaviour of the parties to date. It may even be helpful for the experts to work together to help frame the questions that they should each address and agree methodology and terminology in advance of preparing their reports, if expert evidence is to be admitted.

[78]It is not necessary to deal with the claimants’ other points which in any event were makeweights. Disposal

[79]The parties are to provide written submissions on disposal by 2pm on the 10th October, bearing in mind that they have had the embargoed draft in confidence before then and the need to make progress so as not to jeopardise next year’s MFD hearing. I propose dealing with disposal on the papers. If any party requires a hearing they must say so and explain why they consider it necessary and provide a time estimate for the length of hearing sought (agreed if possible). Miscellaneous matters

[80]There are just a few further observations to be made.

[81]Ms Criddle had diligently combed the transcript of the hearing to seek to identify observations by the EJ in support of her arguments. My primary focus however has been on the judgments themselves, and I did not find it helpful to subject the transcript of a tribunal hearing to forensic textual and linguistic analysis to bolster an appeal of this type This is not a bias appeal and there is no criticism of the EJ’s conduct or behaviour during the hearing. . The ET Rules are explicit that “The Tribunal must seek to avoid undue formality and may itself question the parties or any witnesses so far as appropriate in order to clarify the issues or elicit the evidence.” (r.41(2) ET Rules of Procedure 2024).

[82]It is perfectly natural for the judge to discuss and explore the issues with the representatives at a hearing and it was unhelpful to be taken to comments by the EJ during the course of the hearing that he quite properly made in order better to understand the parties’ arguments. It is the judgment that is being appealed, not what was said during the hearing by the judge, which the parties accepted could not to be taken as a judge’s reasoning. Judges should not be deterred from intervening during a hearing which they often need to do for any number of reasons. For example, if they do not understand a point being made it is only fair to give a party the opportunity to express themselves more clearly, or the EJ may share preliminary concerns on which they would welcome views to enable the advocates a chance to address them, for example. Parties should be mindful not to inadvertently discourage openness during a hearing by their conduct in appeals.

[83]The practice of an EJ corresponding directly with the parties discussing the meaning of a judgment is strongly discouraged (see Tesco Stores Ltd v Element & Ors

[2025] EAT 112

at [210-212]).

[84]This case has become unwieldy and risks becoming out of control. The length of documents is becoming excessive and there is nothing wrong in principle in the tribunal imposing length limits for documents. The MFD Particulars are just one example. Discipline must be imposed if the parties cannot co-operate sufficiently with each other and it must then be maintained to enable the case to make progress. The parties must do their bit to assist the tribunal to achieve the overriding objective.

Cited in 1 later judgment

Ms S Brierley and others v Asda Stores Ltd: 2406372/2008 and others 2026