David Parsons v Convatec Limited [2026] EWHC 98 (Pat)

[2026] EWHC 98 (Pat)Case No HP-2022-000024
IN THE HIGH COURT OF JUSTICE
BUSINESS AND PROPERTY COURTS OF ENGLAND AND WALES
INTELLECTUAL PROPERTY LIST (ChD)
PATENTS COURT
Venue Royal Courts of Justice, Rolls Building, Fetter Lane,Date 21 January 2026
London, EC4A 1NL
Before
THE HON MR JUSTICE MELLOR
Between
DAVID PARSONSClaimantCONVATEC LIMITEDDefendant
Patrick Green KC and Ben Norton (instructed by Kingsley Napley LLP) for ClaimantBrian Nicholson KC and Chris Aikens (instructed by Freshfields LLP) for DefendantHearing Hearing dates: 13 th& 14 th November 2025Approved JudgmentThis judgment was handed down remotely on 21 January 2026 by circulation to the parties or their representatives by e-mail, with the final approved version released to the National Archives on 23 January 2026..............................THE HON MR JUSTICE MELLOR
[1]This is my judgment from aspects of a two-day CCMC in a claim brought by the Claimant, Dr David Parsons, for an award of compensation under section 40 of the Patents Act 1977 against the Defendant (“Convatec”). As I explain below, there was insufficient time to embark on the costs management of this action and this had to be adjourned to a later date.[2]Convatec is a medical products and technologies company, focused on therapies for the management of chronic conditions, including advanced wound care.[3]Dr Parsons is a chemist and was for about 30 years an employee of Convatec. Although Dr Parsons is named as an inventor on numerous patents belonging to Convatec, in this action Dr Parsons focusses on seven patent families for which patents have been granted and alleges that those patents (or the inventions or the combination of both) are of outstanding benefit to Convatec.[4]It is common ground between the parties that the seven patent families at issue can be divided into three groups:(i) Group 1: silverisation (two families; BJP 2002 and Bray 2003),(ii) Group 2: antibiofilm (two families; PBP 2007 and Parsons 2012), and(iii) Group 3: fabric strengthening (three families; BBPT 2013, BBWPST 2014, and P&L 2014).[5]This action began in 2022 and has been before various judges of the Chancery Division previously, most recently before Meade J on 01 May 2025 ([2025] EWHC 1225 (Pat); the “May decision”). I return to Meade J’s May decision where relevant later in this Judgment.[6]As is apparent, these proceedings have been going on for quite some time with considerable costs already expended. Although previous hearings have involved some limited case management, this is the first scheduled case management conference. I am told that Dr Parsons’ and Convatec’s costs to date are £2.4 million and £3.6 million respectively. I acknowledge that Dr Parsons contends his claim to have a value in excess of £10 million. However, as Convatec rightly points out, the greatest compensation awarded in a section 40 claim to date has been £2 million in the Shanks v. Unilever litigation. This is of course in no way determinative for these proceedings, but it is a helpful reminder to keep the big picture in mind when it comes to proportionality for the purposes of case management and the way forward.[7]There were a series of matters for determination at this CCMC, but this Judgment addresses the two most significant applications: i) A strike out application brought by Dr Parsons to strike out parts of Convatec’s Amended Defence. The section of this Judgment below is very largely based on my extempore ruling on 13 November 2025, transcribed by Marten Walsh Cherer Ltd. ii) Whether there should be one five-week trial covering all seven patent families or whether there should be split trials. Convatec argue for a split trial with a first 12-day trial covering all issues on the silverisation families. I rejected the proposal for split trials on 14 November 2025, with reasons to be given later. The second main section of this Judgment contains those reasons.

Dr Parsons’ strike out application

[8]Dr Parsons applies to strike out certain parts of the Amended Defence, pursuant to CPR r.3.4(2)(a), as providing no reasonable ground for defending the claim. Each side set out their arguments in detail in their skeleton arguments and I gave these careful consideration in advance of the hearing. Oral argument lasted about 2 hours (in the morning of the first day of this two-day hearing, with Mr Green’s short reply just after the short adjournment) and, as will appear, was mostly directed to the question I raised at the outset of whether Dr Parsons could demonstrate a material benefit, in cost and case management terms, from the strike out succeeding. During the hearing, I had limited time to give further consideration to these issues. Counsel for Dr Parsons was insistent that a decision on his strike out application was needed before we could proceed to decide Convatec’s application for a split trial (which I was to hear next). I had my doubts about that, but, more generally, there was an urgent need for some active case management of this case and I wished to use as much of the remaining time at this two-day hearing to achieve that.[9]The relevant passages which are sought to be struck out are as follows: i) The last sentence of paragraph 6: “As a matter of law, a claimant cannot rely on an outstanding benefit of patents and/or inventions collectively if they are not of outstanding benefit individually.” ii) The last sentence of paragraph 89, but it is better to see that particular sentence (underlined below) in the context of the paragraph as a whole: ’89. As to paragraph 69, it is admitted that the Claimant is entitled to seek to establish the ‘outstanding benefit’ of any individual Patent, and, in the case of the Later Patents, any Later Patent and/or invention therefor, for the purposes of §§40 and 41 of the Act. The Court should assess a ‘fair share’ of the cumulative benefit of those Patents or Inventions which satisfied the test. Save as aforesaid, paragraph 69 is denied. As a matter of law, however, it is impermissible to seek to establish ‘outstanding benefit’ based on an aggregate benefit allegedly derived from the cumulative effect of multiple patented inventions (and a fortiori from multiple patented inventions / patents as well as other kinds of contribution).’ iii) and paragraphs 90(g) and 103 which refer to paragraph 89.[10]One thing to note is that these two allegations, taken on their own, are not the same. The last sentence of paragraph 6 depends on each individual patent/invention being of outstanding benefit before a cumulative outstanding benefit can be relied upon. By contrast, the last sentence of paragraph 89, viewed on its own does not in terms require each individual patent/invention to have outstanding benefit. The plea is that aggregating benefit from multiple patents/inventions to establish an outstanding benefit is not permissible. Having said that, if paragraph 89 is taken as a whole, the effect is probably as summarised in the last sentence of paragraph 6.[11]These specific pleas need to be viewed in the context of the following features of this case: i) First, Dr Parsons relies on 7 patent families, each of which covers a distinct period in time, with differing overlaps. ii) Second, the fact that, at trial, the Court is going to have to grapple with the issue of construction of the change to section 40 wrought by the amendments which came into force on 1 January 2005. iii) Third, the other pleas in the case and in particular the plea to which Convatec are responding in the passages in question.[12]In the Particulars of Claim under the heading Benefit, the claimant alleges in terms that: ’69. The Court is entitled and invited to consider the benefit of each Patent and/or Invention, and/or to consider the benefit of all (or some) of the Patents and/or Inventions together for the purposes of section 40 and 41 of the Act.’[13]So this plea encompasses the full range of possibilities: the benefit from each individual patent/invention, plus the benefit from every possible combination of patents/inventions, including the benefit from all the patents/inventions. Whilst Dr Parsons must accept, at the very least, that he must establish an outstanding benefit, it is clear that, on his case, the benefits which go to make up an outstanding benefit need not be outstanding themselves.[14]Amongst the list of issues for trial are issues 7 and 8: (7) If none of the Patents / Inventions are individually of outstanding benefit to the Defendant, under s.40(1)(b) of the Act, can the Court consider the benefitof more than one invention or patent (or the combination of both) together? (8) If the answer to issue (7) is yes, is it appropriate for the Court to do so in this case?[15]Counsel for the Claimant contended that if the strike out succeeded, Issue 7 would disappear, since the answer to Issue 7 would be yes. But he accepted that Issue 8 remained – whether it would be appropriate for the Court to consider aggregating the benefit from more than one patent/invention.[16]It follows that aggregation of the benefit of individual patent/inventions is not automatic, the parties accept that the Court has to consider whether it is appropriate, on any given set of facts.[17]The law on strike out is well established and I need not repeat it here. I note that counsel for Convatec has rightly reminded me that the power is discretionary and it is open to me to defer to trial a decision on a claim or issue if satisfied that to do so would further the overriding objective. Counsel for Dr Parsons expressly accepted that the power is discretionary.[18]Dr Parsons says that as these passages in Convatec’s Amended Defence raise a pure matter of statutory construction, it should be determined now as part of Dr Parsons’ strike out application. Dr Parsons argues (and I accept) that determining this would be distinct from any factual considerations (i.e., whether in this case an assessment of aggregate benefit is appropriate).[19]As I have already stated, considerable sums have already been spent by the parties, and coming into this hearing, it is abundantly clear to me that many of the procedural matters that have been and are in dispute are merely satellite litigation that go nowhere to aiding in resolving the underlying dispute between the parties. Coming to this, I have had the overriding objective at the forefront of my mind, and I wanted to be sure that whatever I decided on this application, it would actually help narrow matters and would not just lead to further satellite disputes. Therefore, at the start of this hearing, I put to counsel for both sides the question of whether there is any material benefit if the strike out succeeds.[20]Unsurprisingly, Convatec in both correspondence and evidence had pressed Dr Parsons to identify any material benefit. The responses, such as they were, were less than convincing.[21]Counsel for Dr Parsons argued that there would be material benefit, and put his case two ways: i) If Dr Parsons were to succeed on strike out, there would be major case management and costs benefits for him and it may be possible to abandon his case on benefit derived from individual patents/inventions. This, says counsel for Dr Parsons, could be achieved through notices to admit, part 36 offers, etc to Convatec, which Convatec may be amenable to having lost on a point of law to do with the general impermissibility of aggregation. ii) If Dr Parsons’ application to strike out were to fail, then he would have clarity that aggregation is impermissible and he should abandon that aspect of his case (again with case management / costs benefits).[22]There was also a strong hint in the submissions made by Counsel for Dr Parsons that the outcome of the strike out might have a big effect on external funding for Dr Parsons’ case. Perhaps the most striking material benefit he identified on Dr Parsons’ side was that the strike out would help to identify whether the case was worth the risk.[23]Superficially, Counsel’s arguments on material benefit might seem attractive. However, Dr Parsons’ points on what would happen if his strike out were to fail reveals the fallacy in what he is seeking to achieve on this application.[24]If I were to reject his application, I would not be making a positive finding that aggregation is impermissible. At its highest, all I would be finding is that Dr Parsons has not satisfied the strike out standard. Further, counsel for Convatec rightly made the point that there is no application from Convatec before the Court for a ruling that aggregation is impermissible.[25]What became increasingly clear to me was that this strike out was in fact an invitation to construe section 40 by way of a preliminary issue. However, what Dr Parsons’ application would in fact achieve would be a hybrid, the effect of which would be to determine that Convatec could not run the pleas identified as a matter of law, but leave it open (on the other side of the coin, so to speak) to Dr Parsons to continue to run the full range of options alleged in paragraph 69. Alternatively, it might be an invitation also to decide positively as a matter of law that section 40 admits of the full range of possibilities set out in paragraph 69. I hardly need point out that no such preliminary issue is before me, not least because there has been no order that such a preliminary issue should be decided.[26]Furthermore, on further consideration it is clear that my initial indication that I wanted to explore the possible benefits of the strike out, involved the issues (or some of them) which would normally be considered when deciding whether to order a preliminary issue.[27]Counsel for Dr Parsons sought to argue that the fact that there was no preliminary issue before me did not matter, as, for the purposes of assessing whether there is no reasonable ground to argue impermissibility, I would necessarily have to decide on the proper statutory construction, which he says is a binary issue. That does not follow, in my view. As counsel for Convatec highlighted, there is nuance in their impermissibility argument, and there are circumstances in which even if I were to dismiss the strike out application having considered the statute, Dr Parsons will remain able to advance his plea (in paragraph 69) i.e. his cases on aggregate benefit.[28]I am also suspicious that any finding that I might make on the alleged lack of reasonable grounds under this strike out application will likely only lead to further satellite litigation as to what one or both parties is/are permitted to plead.[29]As to material benefit that would be gained if I were to grant the strike out, I do not see how there could be any major case management or costs benefits. It is clear from the argument I heard in the afternoon of day one on Convatec’s recent requests for further information of both the Re-Re-Amended Particulars of Claim and Dr Parsons’ Reply that at some stage, after review of a considerable amount of financial and other information which will have to be produced by Convatec, Dr Parsons will have to state, in far more detail, his case on benefit generally and the derivation of relevant benefits. Unless or until that narrowing of Dr Parsons’ case takes place, he will (as things stand) continue to run the full range of possibilities embodied in his positive plea in [69] of his Re-Re-Amended POC. In this regard, I was shown Convatec’s Confidential Financial Schedule, but it is clear that considerably more information and analysis will be required before Dr Parsons will be able to state his case on benefit with more particularity.[30]I invited counsel for Dr Parsons to indicate whether he would abandon some or all of this part of his case if I were to grant the strike out. With no criticism to him, counsel for Dr Parsons was not able to provide me with an indication on those terms, but rather deferred the matter, saying that it would require liaising with the other side to see how they would be planning to run their case following the successful strike out.[31]Counsel for Convatec in his submissions on this made clear that notwithstanding a successful strike out on the terms sought by Dr Parsons, they would still be running a case that on the facts of this case aggregation was inappropriate.[32]This, as a litmus test, makes clear to me that there is highly unlikely to be any material benefit gained from this strike out application, even if it is assumed it succeeds.[33]Counsel for Dr Parsons argued that the authorities which make it clear it is unwise to determine ‘short points of law’ in an area of developing jurisprudence, have no application here. He argued strongly that his strike out did not depend on or require consideration of any particular factual matrix. I can see some force in that, but I remain unpersuaded that such a difficult point of law on this difficult section should be considered in a vacuum or on a series of examples dreamt up in submissions. So much is riding on this point of construction of section 40 that it is not unrealistic to assume that the point, if decided, would be appealed to the Court of Appeal and the UK Supreme Court.[34]Dr Parsons’ argument may well turn out to be correct, but I remain of the view that the prudent course is to leave all issues of construction of section 40 to the trial, to be determined on the basis of the facts found at that trial.[35]Counsel for Dr Parsons argued that if disaggregation remained in issue, it would produce a nightmare set of issues for trial. Whether that is so remains to be seen, because the Court is entitled to expect the parties to narrow their cases as trial approaches and to abandon pleas which, on further consideration, look weak or hopeless. However, aggregation of benefits remains part of Dr Parsons’ pleaded case and his case also includes all other possibilities, including disaggregation. It remains up to him whether he sees any benefit in pursuing every plea which his paragraph 69 encompasses and/or there is further case management from the Court.[36]Overall, it seems to me that if, as he does, Dr Parsons is running every possible combination encompassed in paragraph 69, I should not shut Convatec out from arguing against each such combination.[37]As I say, the extreme ends of these combinations may well turn out to be either irrelevant at trial or dropped in advance of trial because they do not provide a route to success for the party who has adopted them.[38]In all the circumstances, I exercise my discretion under CPR 3.4(2)(a) to refuse Dr Parsons’ application.

Single trial or Split trials?

[39]In the morning of the second day of this hearing, I heard argument on Convatec’s proposal for a split trial. As indicated above, at the conclusion of submissions I announced my rejection of their proposal. Since there were numerous other issues which needed resolution before the conclusion of the hearing, I indicated I would give my reasons later and these follow.[40]Convatec apply for this action to be tried in two trials. They set out their proposed split in a schedule to the draft Order for directions which identified the issues to be determined at their first suggested trial. In essence, the proposal is that the Court should determine all the issues from the ‘Group 1 patents’ (i.e. the silverisation patents in the BJP 2002 and Bray 2003 patent families), with the Group 2 and Group 3 patents comprising the other five patent families being dealt with in the second trial. That summary oversimplifies the effect of the split and it is necessary to appreciate the detail of Convatec’s suggested List of Issues for the First Trial:
‘Definitions In this List of Issues: Patents means the granted patents listed in Re-Re-Amended Schedule 1 to Re-Re-Amended Particulars of Claim / Amended Schedule 1 to the Amended Defence for the relevant patent family; and Invention means the invention for which the relevant patent was granted. (A) INVENTORSHIP - section 40(1)(a) 1. Did the Claimant make the following Inventions (Defendant's position in brackets): (a) BJP 2002: jointly with Elizabeth Jacques (or not at all)? (b) Bray 2003: solely (or not at all)? 2. What was the nature of the Claimant’s contribution to the Inventions? (B) BENEFIT / OUTSTANDING BENEFIT – SECTION 40(1)(B) 3. What are the Defendant’s undertakings for the purposes of s.40(1)(b) of the Act? 4. What is the size and nature of those undertakings? 5. What benefit, in money or money’s worth, has the Defendant derived, or may reasonably expect to derive up until the expiry, surrender or revocation of the Patents, from each of: (a) the BJP 2002 Patents; (b) the Bray 2003 Patents; in each case, considered individually? 6. In each case, having regard among other things to the size and nature of the Defendant’s undertaking, is that benefit, taken individually, outstanding to the Defendant? 7. If neither (a) the BJP 2002 Patents nor (b) the Bray 2003 Patents are individually of outstanding benefit to the Defendant, under s.40(1)(b) of the Act, can the Court consider the benefit of both patent families (or the combination of both) together? 8. If the answer to issue 7 is yes, is it appropriate for the Court to do so in this case? 9. If the answer to issue 8 is yes: (a) What benefit, in money or money’s worth, has the Defendant derived, or may reasonably expect to derive up until the expiry, surrender or revocation of the Patents, from the BJP 2002 Patents and the Bray 2003 Patents taken together? (b) Having regard among other things to the size and nature of the Defendant’s undertaking, is that benefit, taken together, outstanding to the Defendant? (C) JUSTICE OF AN AWARD – SECTION 40(1)(C) 10. If the requirements of ss.40(1)(a) and (b) are satisfied, is it just, by reason of the facts found in relation to those requirements, that the Claimant should be awarded compensation to be paid by the Defendant? (D) FAIR SHARE – SECTION 41 11. If the requirements under s.40(1) are satisfied, having regard, among other things, to the matters listed in s41(4) of the Act, what, if any, is the fair share of the benefit to be awarded to the Claimant?’
In this List of Issues: in each case, considered individually?

Background

[41]Before addressing the merits of Convatec’s latest proposal, it is relevant to point out that since the very early stages of this action, Convatec have made proposals to Dr Parsons as to how the extensive scope of his claim should be case managed. In June 2024, Convatec proposed a series of technical trials to determine the nature of each invention and Dr Parsons’ contribution, followed by a single ‘non-technical’ trial to determine ‘outstanding benefit’, compensation and fair share. No progress had been made on that proposal by the time of a hearing before Meade J. on 1 May 2025.[42]Unsurprisingly, Meade J. encouraged further discussion on this issue, saying the following in his judgment:
‘41. Towards the end of the oral argument, I canvassed with counsel how it might be that these proceedings would be managed in terms of trials. I express no concluded view and it would be impossible to do so anyway until the steps that I have already indicated have been taken, but there is an obvious difficulty in terms of the sheer length of the trial in dealing with all of the seven patent families in one trial. I do not intend to make any prescriptive ruling about this today, but I do require the parties to engage in discussions which can begin as soon as possible, but I think cannot be hoped to reach fruition until the pleadings are in more complete form, about how to do that. 42. This exercise should be considered along all axes and I mean that the parties need to have regard to which of the patent families are the most important commercially, which will be the easiest to determine the facts about, which will be most easily characterised in terms of contribution, and so on. A suggestion was made by Convatec, through its solicitors, some time ago which was not taken up, which I think is unfortunate. I think the sooner this discussion at least begins the better. For the moment, I will leave it to the good sense of the parties to work out how to conduct that discussion. It may be that they want to or may feel it is best to initially have that discussion without prejudice to see if it offers a way through, because I think there may well be an integration between that exercise and the consideration, if it is to happen again, of possible settlement. For example, it may be that simply trying to characterise Dr. Parsons's contribution, if any, in relation to the inventions of some of the patents, without considering the remedies that might follow from it, will not progress matters towards a settlement because it will not enable the parties to begin to get a grip of the sums, if any, that are at stake. In any case, this will be a complicated and multi-stage exercise. It will be one of the most crucial decisions to be made at the CCMC in November and, as I say I make no prescriptive decision about it, but I encourage the parties to begin the discussions as soon as possible.’
[43]I was also told that at the hearing Meade J also expressed concerns with any arrangement whereby Dr Parsons could “have a bunch of technical trials and win them all and still not have any money” and that “punting [any potential financial recovery] off into the far future is obviously not likely to be attractive”.[44]Dr Parsons’ position has been throughout that the entire case should be addressed in a single trial, which both parties estimate will require 5 weeks in Court.[45]In the course of argument, I put to Dr Nicholson KC, Convatec’s Counsel, a series of difficulties which I had identified with the proposal. It is fair to say that Dr Nicholson acknowledged that the proposal was not perfect and hinted that it was the best proposal they could come up with in the light of Meade J.’s encouragement. I should add that I would be very much in favour of some division of all the issues to reduce the burden on the Judge of having to deal with everything at a five-week trial, but only if a suitable division could be identified.

Applicable Legal Principles

[46]The power to order a split trial was not in dispute (see CPR 3.1(2)(g), (j) & (k) and see, to similar effect, paragraph 7.5 of the Patents Court Guide). In addition, there was no dispute as to the guidance in the caselaw (summarised in the notes in the White Book at 3.1.10), albeit naturally each side placed emphasis on different parts. Convatec placed emphasis on the statement in the notes that ‘trying one issue separately can sometimes lead to huge savings in costs and delays if that issue is or may be determinative of the whole proceedings, or if a court’s decision upon it is likely to assist the parties to resolve other issues by way of settlement or ADR.’[47]I found it helpful to keep in mind the summary of relevant considerations as set out by Peter MacDonald Eggers KC (sitting as a Deputy Judge of the High Court) in Jinxin Inc v Aser Media Pte Ltd and others [2022] EWHC 2431 (Comm) at [22]-[26]: ‘22. In Electrical Waste Recycling Group Ltd v Philips Electronics UK Ltd [2012] EWHC 38 (Ch), at para. 5-7, Hildyard, J said that the Court should adopt an “essentially pragmatic balancing exercise in assessing how the case is likely to unfold according to whether there is or is not a split”. The judge identified the relevant considerations to be taken into account amongst all of the facts of the case which guide the Court’s discretion in this respect (see also Daimler AG v Walleniusrederierna Aktiebolog [2020] EWHC 525 (Comm), at para. 25-32). The considerations identified by the learned judge, which I have adapted, include:(1) Whether the prospective advantage of saving the costs of an investigation of the issues to be determined at a second trial if the determination of the first trial renders it unnecessary to determine such issues outweighs the likelihood of increased aggregate costs if a further trial is necessary.(2) What are likely to be the advantages and disadvantages in terms of trial preparation and management?(3) Whether a split trial will impose unnecessary inconvenience and strain on witnesses who may be required in both trials.(4) Whether a single trial to deal with all issues will lead to excessive complexity and diffusion of issues, or place an undue burden on the Judge hearing the case.(5) Whether a split may cause particular prejudice to one or more of the parties (for example by delaying any ultimate award of compensation or damages).(6) Whether there are difficulties of defining an appropriate split or whether a clean split is possible.(7) What weight is to be given to the risk of duplication, delay and the disadvantage of a bifurcated appellate process?(8) Generally, what is perceived to offer the best course to ensure that the whole matter is adjudicated as fairly, quickly and efficiently as possible?(9) Whether a split trial would assist or discourage mediation and/or settlement. 23. The fact remains that the decision to split what would otherwise be a single trial into more than one trial each dealing with defined issues is a step out of the norm, where in most cases there will be a single trial determining all of the issues arising in an action. Accordingly, there must be a real and substantial advantage if a split trial were ordered to take place. In Bindel v PinkNews Media Group Ltd [2021] EWHC 1868 (QB); [2021] 1 WLR 5497, Nicklin, J said at para. 33: “a case in which the court directs determination of a preliminary issue that will require resolution of disputed issues of fact, including disclosure, witness statements and cross-examination, must be regarded as an exception to the general rule, and one that requires careful consideration by the court and very clear justification.” 24. It is also salutary to recall the warning of Lord Neuberger, MR in Rosetti Marketing Ltd v Diamond Sofa Company Ltd [2012] EWCA Civ 1021; [2013] 1 All ER (Comm) 308, at para. 1 in connection with the proposal for trials of preliminary issues: “… It represents yet another cautionary tale about the dangers of preliminary issues. In particular, it demonstrates that (i) while often attractive prospectively, the siren song of agreeing or ordering preliminary issues should normally be resisted, (ii) if there are none the less to be preliminary issues, it is vital that the issues themselves, and the agreed facts or assumptions on which they are based, are simply, clearly and precisely formulated, and (iii) once formulated, the issues should be answered in a clear and precise way.” 25. Although the present application was not for a trial of preliminary issues, at least nominally, the Master of the Rolls’ warning remains relevant where a party applies for specific issues to be determined separately from the majority of issues arising in the action, based on limited evidence and specified assumptions to be made. 26. Unless a split trial can be justified as a means of resolving the disputed issues in action in accordance with the overriding objective with clear benefits over and above those of a single trial, the peril exists that a split trial will add considerably to the parties’ costs burden, will delay the conclusion of the action (with an unappealing drain on the Court’s resources) and/or will lead to unanticipated difficulties.’ (1) Whether the prospective advantage of saving the costs of an investigation of the issues to be determined at a second trial if the determination of the first trial renders it unnecessary to determine such issues outweighs the likelihood of increased aggregate costs if a further trial is necessary. (2) What are likely to be the advantages and disadvantages in terms of trial preparation and management? (3) Whether a split trial will impose unnecessary inconvenience and strain on witnesses who may be required in both trials. (4) Whether a single trial to deal with all issues will lead to excessive complexity and diffusion of issues, or place an undue burden on the Judge hearing the case. (5) Whether a split may cause particular prejudice to one or more of the parties (for example by delaying any ultimate award of compensation or damages). (6) Whether there are difficulties of defining an appropriate split or whether a clean split is possible. (7) What weight is to be given to the risk of duplication, delay and the disadvantage of a bifurcated appellate process? (8) Generally, what is perceived to offer the best course to ensure that the whole matter is adjudicated as fairly, quickly and efficiently as possible? (9) Whether a split trial would assist or discourage mediation and/or settlement. “a case in which the court directs determination of a preliminary issue that will require resolution of disputed issues of fact, including disclosure, witness statements and cross-examination, must be regarded as an exception to the general rule, and one that requires careful consideration by the court and very clear justification.” “… It represents yet another cautionary tale about the dangers of preliminary issues. In particular, it demonstrates that (i) while often attractive prospectively, the siren song of agreeing or ordering preliminary issues should normally be resisted, (ii) if there are none the less to be preliminary issues, it is vital that the issues themselves, and the agreed facts or assumptions on which they are based, are simply, clearly and precisely formulated, and (iii) once formulated, the issues should be answered in a clear and precise way.” Convatec’s arguments[48]Convatec submitted that their proposal would be likely to save time, costs and court resources. They held out the prospect that the parties would be able to resolve all remaining issues in the action following the first trial, such that it would not be necessary for the parties to prepare, or the court to determine the remaining issues in the case.[49]Convatec’s comparison of the two alternatives can be summarised as follows: i) A 25 day trial vs a first trial of 12 days. ii) A likely costs difference of £5m (future costs of £11.4m vs £6.2m).[50]In terms of the advantages of the first trial, and the consequent prospect of settlement following it, Convatec contended as follows: i) First, as all issues relating to the two patent families will be addressed at the first trial, if Dr Parsons is successful, the court will make an award of compensation in his favour. This specifically addresses Meade J’s concern at [41] of his judgment quoted above that a technical / non-technical trial split of the issues would not enable the parties to get a grip on the sums involved. It also specifically addresses the concerns the Judge expressed at the last hearing implicitly encouraging a trial structure which does not inherently mean that even if Dr Parsons wins at the earliest trial(s), he will not be able to obtain any relief (until some later trial). ii) Second, the first trial will cover almost all of the points of principle which are at large between the parties, namely the proper approach to s.40 in terms of “outstanding benefit”, “justice”, “fair share” and so on, including the proper approach to aggregation of any benefit from multiple patents. As the Court will appreciate, there is very little existing authority on any of these matters, and much of the statutory scheme will need to be addressed in significant detail. Having done so, and the Court having ruled in the first trial, the scope for rearguing the same issues of principle at a second trial are likely to be limited. The only point of principle of which we are aware which would not be ventilated in the proposed first trial is the consequence of the post-2005 amendment to s.40 (as this only applies to the patent families in Groups 2 and 3). iii) Third, the two silverisation patent families are commercially the most valuable to Dr Parsons. He asserts in paragraph 44 of the RRAPoC, that those families are “essential to the success of all of the Defendant’s products containing silver” [B1/2/28]. That is not accepted by Convatec, but no such allegation is made by Dr Parsons in respect of any patent family in Groups 2 and 3. According to Dr Parsons, Group 1 accounted for 30% of Convatec’s total profit from its Advanced Wound Care Division in 2019, exceeding the profits generated by the products that are alleged to utilise the inventions of the other groups. As such, trying these patent families first gives Dr Parsons the opportunity to access the largest potential benefit pool at the earliest possible stage. iv) Fourth, the two silverisation families are the earliest in time. It is logical to take those two first given the evolution of the Aquacel product lines whereby Convatec contends that later products cannibalised sales of earlier ones. It ensures that all relevant findings of fact for the assessment of Group 1 are made in trial 1, and also ensures that the findings of fact from the first trial are available to form the necessary starting-point for any further assessment of Groups 2 and 3 (be that during settlement negotiations, or at any subsequent trial).[51]Convatec stressed what they characterised as the limited differences between the Group 2 & 3 issues vs Group 1, being only: i) any change as a result of the 2005 amendment to s.40; ii) the specific facts of inventorship for those families; and iii) the specific calculations in relation to contribution (given different groups of Aquacel products are relied on for different families).[52]Accordingly, Convatec argued that there seems a strong possibility that the parties will be able to resolve the outstanding disputes. But even if they cannot, the issues remaining to be determined will have narrowed very significantly and that it is highly likely that the remaining issues on Groups 2 and 3 can, together, be tried in substantially less time (and with less expense) than the first trial on Group 1. Analysis[53]I should say at the outset that my consideration of this application was greatly assisted by the Confidential Financial Summary which Convatec served in September 2025. Part A sets out figures for the global revenue from 2002 to 2024 for 11 groups of products in the Aquacel range, although the Summary does not include figures for the Aquacel base product i.e. before silver was introduced. The dates when various products started generating revenue very roughly correspond (with a suitable delay) to the dates of the patent families in issue. 10 of the 11 product lines include silver, but the product line which does not include silver was a major contributor to revenues from 2014 onwards. As I mentioned in the course of argument, when the later products come on stream (the ‘Extra’ and ‘+’ product lines in particular), there are significant drops in the revenues generated by the Aquacel Ag base product line. I should add that to simplify matters, submissions proceeded on the assumption that ‘+’ signified Group 2 and ‘Extra’ Group 3. The figures suggest(a) significant cannibalisation of the revenues of earlier product lines by later ones (as one would expect, since Convatec would emphasise the benefits of their new product lines in marketing) and(b) overall revenues follow a continuum.[54]These observations caused me to pose this important question to Dr Nicholson KC: in essence, if we take account of silverisation in the first trial, how do we divide the revenues (and profits) from the later ‘Extra’ and ‘+’ product lines, nearly all of which (save one) include silver. His answer was that we would have almost 10 years of performance of Aquacel Ag as a guide before the additional product lines came on stream. That is all very well, but provides no solution to the cannibalisation. Dr Nicholson suggested that expert evidence from industry and market experts would assist, but acknowledged that the parties had not even started investigating how these issues could be tackled. That caused me to observe that there was no pleading on either side as to how to go about tackling these issues.[55]Even if there was a feasible way to address those issues, this analysis demonstrates very clearly indeed that the proposal for the first trial does not come close to proposing a clean split of issues. Nor, in my view, on the current information, can there be any realistic expectation of anything approaching a clean split of issues, in view of the continuum in the global revenue figures.[56]In his submissions, Mr Green KC reinforced the difficulties I had already canvassed in argument but also drew attention to further difficulties resulting from(a) the effect of the 2005 amendments to s.40; and(b) decisions being made in the first trial which would undoubtedly impact on the Group 2 and 3 patent families without their factual matrix being taken into account, including the benefits attributable to the ‘+’ and ‘Extra’ features, as opposed to the benefit attributable to silverisation. To tease out the full implications of that latter point: the calculation of the benefit, compensation and fair share attributable to silverisation alone in the first trial would necessarily have to involve an apportionment between Ag, ‘+’ and ‘Extra’ for all the later products. With the evidence and findings on the ‘+’ or ‘Extra’ products (benefits, compensation & fair share) apparently being reserved to the second trial, it is extremely difficult to see how a reliable apportionment could be made at the first trial and even if one were made, there would be a significant risk that it would require modification at the second trial. These (and other points) are merely the consequence of the fact that there is plainly no clean split of issues which can presently be identified.[57]Having said all that, I did not rule out the possibility that, on further investigation, the parties might be able to identify a clean enough split, but, as I indicated, a lot more work needs to be done before that could be identified.[58]Mr Green KC also identified additional problems including the strain on fact witnesses having to give evidence at both trials and the difficulties in analysis for the experts, let alone the judge, particularly on the aggregation arguments: at which trial would they be considered?[59]Leaving aside the trial difficulties, Convatec’s hope that the parties would be able to settle in the light of the findings made at the first trial struck me as extremely optimistic, if not wholly unrealistic, bearing in mind the revenues generated by the later product lines. Indeed it would be more realistic to assume that there would be an appeal (or possibly appeals by both sides) from the judgment in the first trial, with consequent effects on the timing and preparation for the second trial.[60]I was also struck by the fact that Convatec (with deeper pockets) proposed this split which Dr Parsons firmly resisted. Conclusion on the split trial proposal[61]Overall, I concluded that the split trial proposal would be likely to lead to the whole dispute taking much longer to resolve, at much greater cost. Indeed, I concluded this was a textbook example where all the warnings in the caselaw would be violated and all the downsides would come to pass. That is why I was able to announce my rejection of the split trial proposal at the hearing.

Other matters

[62]Other case management issues concerning Requests for Further Information, a dispute over expert evidence and disputes over disclosure were resolved during the hearing. However, there was insufficient time to tackle costs budgeting of this action, and that will have to return to Court in early 2026.[63]I should add that, following my encouragement to the parties to cooperate, they agreed a confidentiality regime and a comprehensive directions order (which included some provisions which had not previously been ventilated). I trust that this degree of cooperation in moving this action forward in a cost-effective and proportionate way will continue.