“38. . . . it is the oddities of this case which weigh heavily in the broad, merits-based judgment which the court must make. Had the Claimant raised Objection 1 before the preliminary issues hearing, the Costs Judge may have expressed the view quoted at paragraph 17 above or she may have been persuaded by the Claimant’s argument or expressed no view. However, it would not have resulted in a different order. The order was based on the finding that the Defendant had repudiated the retainer. The result of the preliminary issues hearing would have been the same. 39. On an appeal from the order, Trower J’s conclusion that the client had repudiated the agreement would not necessarily have resulted in a decision as to the consequences of that conclusion. He may well have left it to the costs judge, as he left the Claimant’s argument that CFAs 2 and 3 are unenforceable on the grounds of illegality. 40. That itself is significant. Although the illegality issue has since been abandoned, as at the conclusion of the appeal before Trower J there was still an outstanding issue as to liability. 41. The Claimant can be fairly criticised for not raising Objection 1 earlier. However, there would still have been a preliminary issues hearing and there would still have been an appeal. It may be that some of the costs since the appeal would have been avoided, but any prejudice caused by that can be remedied in costs. 42. Raising the objection in the points of dispute simply followed Trower J’s conclusion on repudiation. I cannot conclude that raising it in that way at that time involved unjust harassment of the Defendant. In all the circumstances, I cannot say that it is an abuse of process.”
“63. Where solicitors have accepted the risk that they may be entitled to no fees at the end of the case, it is not clear that they should have the right to deliver a bill where the retainer is determined before the end of the case. In my experience there are similar provisions to clause 14.3 in most conditional fee agreements, almost certainly for this reason. 64. In the present case, at the point of termination, the solicitors had a choice. They could “stick” and elect for their basic fees and disbursements under clause 14.3 (but lose the success fee) or they could “twist” and claim damages for their loss of basic fees and success fees. 65. In my judgment the Defendant was not entitled to deliver the 2016 bill and the Claimant was not liable to pay it. Trower J has already found that there was no right to payment of the 2012 bill at the time that it was delivered. 66. The purpose of a Solicitors Act assessment is to determine the amount payable by the client in respect of the bill which is the subject of the order for assessment. If nothing is payable when the bill is delivered, the bill must be assessed at nil.”
“Where the retainer is terminated following repudiation by the client (which we now know to be the case) is the solicitor entitled to payment of his fees for work done up to the date of termination if the retainer was a conditional fee agreement and no success fee had been achieved?”
“25. . . i) CFA-3 defined “winning the claim” as the case where Global Energy’s claim was finally decided in its favour: (clause 1 (definitions)). ii) If Global Energy “won”, it would be liable for Rosenblatt’s fees at the normal rates, together with disbursements and the “Success Fee”: (clause 5.1). The Success Fee was a percentage uplift (clause 1 (definitions)) set at 100% of Rosenblatt’s normal rate fees (clause 7.1)). iii) If Global Energy “lost” (which comprised all cases where Rosenblatt did not “win”), then Rosenblatt would retain an “Advance Fee” of£300,000 and Global Energy would be liable for any outstanding disbursements: (clause 6). 26. It was common ground between the parties that there had been no “win” within the meaning of clause 5.”
“34. . . . i) Rosenblatt could have ended CFA-3 in reliance upon clause 14.3. ii) However, Rosenblatt did not avail itself of clause 14.3, so as to bring CFA-3 to an end and thereby cause an obligation on Global Energy to pay Rosenblatt’s fees up to that date and any disbursements to accrue. iii) As a result, no obligations accrued against Global Energy.”
“50. . . Rosenblatt rightly submitted that the fact that a contract had – as here – been brought to an end and discharged by virtue of a breach of contract was a material factor when considering a remedy in unjust enrichment. In Photo Production Ltd v. Securicor Transport Ltd,[1980] AC 827 at 849, Lord Diplock described the effects of an accepted repudiatory breach: Where such an election is made (a) there is substituted by implication of law for the primary obligations of the party in default which remain unperformed a secondary obligation to pay monetary compensation to the other party for the loss sustained by him in consequence of their non-performance in the future and (b) the unperformed primary obligations of that other party are discharged… Lord Diplock made clear that these secondary obligations consequent on breach could be “excluded or modified by the express words of the contract” (at 849).”
“51. There is, thus, no category difference between unjust enrichment claims where the contract is discharged and those cases where the contract is regularly performed. The test remains the same. Of course, it is far harder for a contract to anticipate, and cater for, the circumstances arising in a case of breach; and that is why claims in unjust enrichment where the unjust factor is failure of basis are much more common in the case of discharged contracts. A vacuum can be created, where benefits are conferred in circumstances where there is no contractual risk allocation or no Obligation Rule to constrain the restitutionary remedy.”
“53. CFA-3 made detailed provision in anticipation of problems arising prior to the Claim’s resolution in clause 14. In one sense, it was a complete code in that it anticipated a number of risk contingencies: (i) “buyer’s remorse”, where Global Energy wanted to stop the proceedings; (ii) “rejection of settlement advice”, where there is an offer to settle, which (contrary to advice) Global Energy refuses; (iii) “client’s non-performance”, where Global Energy fails to perform its clause 13 responsibilities; and (iv) “seller’s remorse”, where Rosenblatt come to the view that Global Energy no longer has reasonable prospects of success. 54. In another sense, clause 14 is not a complete code, because of course the common law remedy of damages for repudiatory breach of contract remains, in addition to the clause 14 “code”
“(a) the appeal would – (i) have a real prospect of success; and (ii) raises an important point of principle or practice; or (b) there is some other compelling reason for the Court of Appeal to hear it.”
“The bringing of a claim or the raising of a defence in later proceedings may, without more, amount to abuse if the court is satisfied (the onus being on the party alleging abuse) that the claim or defence should have been raised in the earlier proceedings if it was to be raised at all. I would not accept that it is necessary, before abuse may be found, to identify any additional element such as a collateral attack on a previous decision or some dishonesty, but where those elements are present the later proceedings will be much more obviously abuse, and there will rarely be a finding of abuse unless the later proceedings involves what the court regards as unjust harassment of a party. It is, however, wrong to hold that because a matter could have been raised in earlier proceedings it should have been, so as to render the raising of it in later proceedings necessarily abusive. That is to adopt too dogmatic an approach to what should in my opinion be a broad, merits-based judgment which takes account of the public and private interests involved and also takes account of all the facts of the case, focusing attention on the crucial question whether, in all the circumstances, a party is misusing or abusing the process of the court by seeking to raise before it the issue which could have been raised before. As one cannot comprehensively list all possible forms of abuse, so one cannot formulate any hard and fast rule to determine whether, on given facts, abuse is to be found or not. . . While the result may often be the same, it is in my view preferable to ask whether in all the circumstances a party’s conduct is an abuse that to ask whether the conduct is an abuse and then, if it is, to ask whether the abuse is excused or justified by special circumstances.”
“It is one thing to refuse to allow a party to relitigate a question which has already been decided; it is quite another to deny him the opportunity of litigating for the first time a question which has not previously been adjudicated upon. This latter (though not the former) is prima facie a denial of the citizen’s right of access to the court conferred by the common law and guaranteed byarticle 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms (1953). While, therefore, the doctrine of res judicata in all its branches may properly be regarded as a rule of substantive law, applicable in all save exceptional circumstances, the doctrine now under consideration can be no more than a procedural rule based on the need to protect the process of the court from abuse and the defendant from oppression.”
“the inherent power which any court of justice must possess to prevent misuse of its procedure in a way which, although not inconsistent with the literal application of its procedural rules, would nevertheless be manifestly unfair to a party to the litigation before it, or would bring the administration of justice into disrepute amongst right-thinking people.”
“an appellate court will be reluctant to interfere with the decision of the judge in the judgment he reaches on abuse of process by the balance of the factors; it will generally only interfere where the judge has taken into account immaterial factors, omitted to take account of material factors, erred in principle or come to a conclusion which was impermissible or not open to him.”
“46. There can be no doubt, therefore, that both Henderson v Henderson and Johnson v Gore-Wood are primarily concerned with a party seeking to raise in subsequent proceedings an issue which had either already been decided in earlier proceedings, or which could and should have been raised in those earlier proceedings. However, it is not necessary for there to be two different sets of proceedings for the rule to apply. If a single set of proceedings involved a binding determination at an earlier stage, then the rule in Henderson v Henderson may apply to subsequent stages of the same litigation. Thus, in Seele Austria GmBH v Tokio Marine Insurance Ltd[2009] EWHC 2505 (TCC) , the judge refused to allow the claimant to amend its pleadings to allege that the defective windows were a matter of design, in circumstances where, at an earlier stage of the litigation, Field J had concluded that the defects were a matter of workmanship, and the same point had been determined by the Court of Appeal. Accordingly, the claimant could not raise a contradictory case by way of a subsequent amendment. 47. It follows that the rule in Henderson v Henderson can apply, not only to one set of proceedings, but to earlier interlocutory decisions in those proceedings: see Seele, and Koza Ltd v Koza Altin Isletmeri AS[2020] EWCA Civ 1018 , [2022] 1170 at [41] – [42] per Popplewell LJ. But it is crucial to remember that, whenever it arises, the rule in Henderson v Henderson requires a previous determination by the court. As Lord Hobhouse put it in In Re Norris[2001] UKHL 34 at paragraph 26: “It will be a rare case where the litigation of an issue which has not previously been decided between the same parties or their privies will amount to an abuse of process”
“(a) 95% of the fees at the normal rates to reflect the risk that Rosenblatt is taking that it will not receive the fees at the normal rates (the conditional fees) if the Client loses (the risk element of the success fee); and (b) 5% of the fees at the normal rates to reflect the postponement of payment of conditional fees until the end of the Claim (the postponement element of the success fee).”
“. . . The Client will not be liable for the Success Fee. Usually, the Client will also be liable for the costs and disbursements of the opponent. The client may be able to take out an insurance policy against this risk (see clause 10 below). In addition, the Client will be liable for any damages and interest awarded or agreed against the client if the Opponent succeeds in any counterclaim against the Client.”
“. . . include giving Rosenblatt full, honest and timely instructions, not asking Rosenblatt to work in an improper or unreasonable way, cooperating fully with Rosenblatt in the preparation of its claim, and paying all amounts due to Rosenblatt within 30 days of receipt of an invoice. “ At clause 13.2, Rosenblatt’s responsibilities are stated to: “include always acting in the Client's best interests, subject to Rosenblatt's overriding duty to the court, explaining to the Client the risks and benefits of taking legal action, giving the Client the best information possible about the likely costs of the Claim and the different methods of funding those costs.”
“The Client can end this agreement in writing at any time. If the Client does not continue with the Claim, the client must pay Rosenblatt's fees at the normal rates for the work done to the termination date and disbursements. If the Client continues with the Claim and wins, the Client will also have to pay the Success Fee for that work.”
“Rosenblatt can end this agreement if the Client rejects Rosenblatt's advice to accept a reasonable offer from the Opponent to settle this Claim. In those circumstances, the Client must pay Rosenblatt's fees for the work done to the termination date and disbursements. If the Client continues with the Claim and wins, the Client will also have to pay the Success Fee for that work.”
“Rosenblatt can end this agreement if the Client does not meet its responsibilities. If this happens, the Client will have to pay Rosenblatt’s fees for the work done to the termination date and disbursements.”
“Rosenblatt can end this agreement if it believes the Client no longer has a reasonable prospect of success. If this happens, the Client will only have to pay Rosenblatt's fees and disbursements.”
“[54] Despite its evolutionary nature, the common law claim in unjust enrichment can, for present purposes, be summarised as follows: a claimant has a right to restitution against a defendant who is unjustly enriched at the claimant’s expense. The purpose of the claim is to correct normatively defective transfers of value, usually by restoring the parties to their pre-transfer positions (see Bank of Cyprus UK Ltd v Menelaou[2015] UKSC 66 , [2016] 2 All ER (Comm) 259,[2016] AC 176 (at [23]) and Investment Trust Companies (in liq)v Revenue and Customs Comrs[2017] UKSC 29 ,[2017] 3 All ER 113 ,[2018] AC 275 (‘ITC’) (at [42]) where Lord Reed went on to comment that it ‘reflects an Aristotelian conception of justice as the restoration of a balance or equilibrium which has been disrupted’). [55] Courts and commentators have broken down the conceptual structure of a claim in unjust enrichment into four elements: (i) Has the defendant been enriched? (ii) Was the enrichment at the claimant’s expense? (iii) Was the enrichment unjust? (iv) Are there any defences? (See Goff & Jones at 1–09.) … [58] It is the ‘unjust factor’ that distinguishes the English claim in unjust enrichment from the civilian ‘absence of basis’ approach. Examples of unjust factors include mistake, duress, undue influence, failure of consideration, necessity and legal compulsion. These unjust factors are recognised because they establish that the claimant did not intend the defendant to receive a benefit in the circumstances, either because the claimant never had an intent to benefit the defendant in those circumstances or the intent was vitiated or qualified in some way. [59] An unjust enrichment claim is not based on a wide ranging and open-ended assessment of fairness (or justice) in the round. Rather, it is a common law remedy requiring a claimant to make out an established category of ‘unjust factor’ in order to trigger the claim. As Lord Sumption put it in Swynson (at [22]), it is ‘not a matter of judicial discretion’, referring to the dictum of Lord Reed in ITC (at [39]): ‘[it] does not create a judicial licence to meet the perceived requirements of fairness on a case-by-case basis: legal rights arising from unjust enrichment should be determined by rules of law which are ascertainable and consistently applied . . .’” ‘[it] does not create a judicial licence to meet the perceived requirements of fairness on a case-by-case basis: legal rights arising from unjust enrichment should be determined by rules of law which are ascertainable and consistently applied . . .’”
“It was thought at one time that a prerequisite to a claim in unjust enrichment was that any relevant contract must, if initially valid, have been discharged for breach or frustration or be void, unenforceable or incomplete (see Goff & Jones The Law ofRestitution (7th edn, 2007) at 1–063 to 1–067; An Introduction to the Law of Restitution at p 464 and Chitty on Contracts (30th edn, 2008) at 29–058). This may have been a consequence of the fact that in almost all cases where a claimant seeks restitution for a failure of basis, any relevant contract will be ineffective. And where a contract has been discharged for repudiatory breach or frustration, the legal enforceability of the contract and the failure of basis are two sides of the same coin.”
“. . As stated in DD Growth Premium by Lord Sumption and Lord Briggs (at [62]): “It is fundamental that a payment cannot amount to an enrichment if it was made for full consideration; and that it cannot be unjust to receive or retain it if it was made in satisfaction of a legal right … The proposition is supported by more than a century and a half of authority …” “It is fundamental that a payment cannot amount to an enrichment if it was made for full consideration; and that it cannot be unjust to receive or retain it if it was made in satisfaction of a legal right … The proposition is supported by more than a century and a half of authority …”
“The Law of Restitution (at p 328) indicates that the exceptions could be rationalised as follows: (i) On the basis that there may be no undermining of the risks undertaken by the parties and so no inconsistency between contract and unjust enrichment; (ii) The very need to establish failure of consideration is sufficient to prevent unwarranted subversion of the contract, because if all parties had known that the consideration would fail, the benefit would never have been conferred.”
“[79] The core concept of ‘failure of basis’ is that a benefit has been conferred on a joint understanding that the recipient’s right to retain it is conditional. If the condition is not fulfilled, the recipient must return the benefit (see Goff & Jones at 12–01). Whilst failure of basis ranks alongside the unjust factors of mistake, duress and undue influence as a factor negativing consent, it differs in that it is concerned with qualification of consent, as opposed to impaired or vitiated consent (see Burrows The Law of Restitution (3rd edn, 2011)).”
“88. Judge Pearce records at para 169 of his judgment that during closing submissions he raised with counsel the decision in MacDonald Dickens & Macklin v Costello[2012] QB 244 (“Costello”). He regarded that case as establishing a principle that the parties’ mutual obligations in a case in which they concluded a contract should be limited to the obligations which they have defined and allocated in the course of negotiating that contract, and that the court should uphold those contractual arrangements (see para 190). In Costello, the claimant builders contracted with a company owned by the defendants for the construction of buildings on land owned by the defendants. The defendants had informed the claimant that for tax reasons they were using their company, Oakwood, to enter into the contract rather than contracting themselves. Oakwood paid the claimant’s first few invoices in full but then stopped paying. The claimant brought a claim in unjust enrichment against the Costellos personally. Etherton LJ (with whom Patten and Pill LJJ agreed) said that there could be no doubt that Mr and Mrs Costello had benefited from, or, in restitutionary terms, had been enriched by, the work carried out by the claimants on the site. He described the point of principle that arose in the following terms: “21. The second point of principle is whether a restitutionary claim should be allowed to undermine the contract between Oakwood and the claimants, that is to say, the way in which the parties chose to allocate the risks involved in the transaction. The parties arranged the transaction as one in which legally enforceable promises were made only between Oakwood and the claimants, even though the benefit of the contract was to be conferred on Mr and Mrs Costello. The obligation to pay for the claimants’ services, and so the risk of non-payment, was contractually confined to Oakwood. If a claim was permitted directly against Mr and Mrs Costello it would shatter that contractual containment. It would also alter the usual consequences of Oakwood’s insolvency, which was one of the risks assumed by the claimants in contracting with Oakwood, since a direct claim against Mr and Mrs Costello would improve the claimants’ position over Oakwood’s other unsecured creditors.” 89. Etherton LJ held that the unjust enrichment against the Costellos must fail (para 23): “The general rule should be to uphold contractual arrangements by which parties have defined and allocated and, to that extent, restricted their mutual obligations, and, in so doing, have similarly allocated and circumscribed the consequences of non-performance. That general rule reflects a sound legal policy which acknowledges the parties’ autonomy to configure the legal relations between them and provides certainty, and so limits disputes and litigation. The following cases support its application to the present case.” 90. An earlier warning against relying on unjust enrichment in circumstances where there is a subsisting contract came from an impeccable source in Pan Ocean Shipping Co Ltd v Creditcorp Ltd (The Trident Beauty)[1994] 1WLR 161 . In that case, Pan Ocean, the time charterer of the vesselwas seeking to recover an instalment of the time charter hire because thevessel had been off hire for the whole period in respect of which the relevanthire instalment was paid. The claim was brought not against the shipownerbut against an assignee of the shipowner’s debt. Lord Goff of Chieveley(with whom Lord Lowry agreed) referred to the “usual practice” in theadministration of time charters that where a vessel was off hire from time totime, an adjustment would be made to the next instalment of hire which felldue. Most time charters include express provision for the repayment of hirebut if necessary a term would be implied into the contract to that effect. Hesaid at p 164E—H: “All this is important for present purposes, because it means that, as between shipowner and charterer, there is a contractual regime which legislates for the recovery of overpaid hire. It follows that, as a general rule, the law of restitution has no part to play in the matter; the existence of the agreed regime renders the imposition by the law of a remedy in restitution both unnecessary and inappropriate . . . “It follows that, in the present circumstances and indeed in most other similar circumstances, there is no basis for the charterer recovering overpaid hire from the shipowner in restitution on the ground of total failure of consideration.” 91. Lord Goff held that the position was no different as regards a claim against an assignee who was a stranger to that contract. He said later (p 166D) that he was well aware that writers on the law of restitution have been exploring the possibility that in exceptional circumstances a plaintiff may have a claim in restitution when he has conferred a benefit on the defendant in the course of performing an obligation to a third party. He went on: “But, quite apart from the fact that the existence of a remedy in restitution in such circumstances must still be regarded as a matter of debate, it is always recognised that serious difficulties arise if the law seeks to expand the law of restitution to redistribute risks for which provision has been made under an applicable contract.” 92. The same principle was applied by the Court of Appeal in Dargamo cited earlier. There, the parties entered into a written agreement for the transfer of certain assets under a share purchase agreement for a consideration of US$950m . The assets were transferred and the consideration paid but the claimants sought to recover a proportion of the purchase price on the basis that the parties’ common understanding when they entered into the contract was that they would subsequently enter into an agreement to transfer other substantial assets, for which some of the US$950m was intended to be an advance payment. That subsequent contract was never concluded and the additional assets were never transferred. The claim in unjust enrichment was dismissed. Despite the common understanding, there had been no failure of basis amounting to an unjust factor and so no trigger to an entitlement to a payment. The parties must be held to the express terms of the contract into which they chose to enter. They had both complied fully with those terms and the law of unjust enrichment did not provide a means of subverting that agreement. 93. In applying these principles in the present case, Judge Pearce observed that our legal system recognises the importance to be given to parties to exercise freedom of choice in contractual negotiations so that courts “will look with scepticism at any attempt to use a principle such as unjust enrichment to redefine their rights and obligations” (para 186).” “21. The second point of principle is whether a restitutionary claim should be allowed to undermine the contract between Oakwood and the claimants, that is to say, the way in which the parties chose to allocate the risks involved in the transaction. The parties arranged the transaction as one in which legally enforceable promises were made only between Oakwood and the claimants, even though the benefit of the contract was to be conferred on Mr and Mrs Costello. The obligation to pay for the claimants’ services, and so the risk of non-payment, was contractually confined to Oakwood. If a claim was permitted directly against Mr and Mrs Costello it would shatter that contractual containment. It would also alter the usual consequences of Oakwood’s insolvency, which was one of the risks assumed by the claimants in contracting with Oakwood, since a direct claim against Mr and Mrs Costello would improve the claimants’ position over Oakwood’s other unsecured creditors.” “The general rule should be to uphold contractual arrangements by which parties have defined and allocated and, to that extent, restricted their mutual obligations, and, in so doing, have similarly allocated and circumscribed the consequences of non-performance. That general rule reflects a sound legal policy which acknowledges the parties’ autonomy to configure the legal relations between them and provides certainty, and so limits disputes and litigation. The following cases support its application to the present case.” “All this is important for present purposes, because it means that, as between shipowner and charterer, there is a contractual regime which legislates for the recovery of overpaid hire. It follows that, as a general rule, the law of restitution has no part to play in the matter; the existence of the agreed regime renders the imposition by the law of a remedy in restitution both unnecessary and inappropriate . . . “It follows that, in the present circumstances and indeed in most other similar circumstances, there is no basis for the charterer recovering overpaid hire from the shipowner in restitution on the ground of total failure of consideration.” “But, quite apart from the fact that the existence of a remedy in restitution in such circumstances must still be regarded as a matter of debate, it is always recognised that serious difficulties arise if the law seeks to expand the law of restitution to redistribute risks for which provision has been made under an applicable contract.”
“. . . When parties stipulate in their contract the circumstances that must occur in order to impose a legal obligation on one party to pay, they necessarily exclude any obligation to pay in the absence of those circumstances; both any obligation to pay under the contract and any obligation to pay to avoid an enrichment they have received from the counterparty from being unjust. The “silence” of the contract as to what obligations arise on the happening of the particular event means that no obligations arise as Lord Hoffmann made clear in Belize cited earlier. This excludes not only an implied contractual term but a claim in unjust enrichment.”
“191. Nevertheless, there is also another broader reason why the existence of a contract precludes a claim based on the law of unjust enrichment. This is that there already exists a system of law for determining what rights and remedies contracting parties have in relation to the subject matter of their contract. It is called the law of contract. In relation to the subject matter of the contract, the law of contract determines, and governs the consequences of, not only the existence but also the absence of an obligation on one contracting party to confer a benefit on the other. To redistribute the allocation of benefits and losses provided for by the law of contract by applying another set of legal principles would undercut this regime.”
“It is however important to observe the limits of the rule. It addresses solely a situation in which as a result of the wrongful termination or repudiation of the agreement the claimant has failed to complete his contractual performance and has in consequence not reached a point where counter-performance by the defendant has become due. It does not apply where the claimant has performed and has in consequence an entitlement under the contract to payment or a remedy in damages. In this I agree entirely with Cooke J in Taylor v Motability Finance Ltd[2004] EWHC 2619 (Comm) .”
“As the law stands in Australia, as it does in England, New Zealand, Canada and the United States, upon termination for repudiation of an uncompleted contract containing an entire obligation (or, as will be seen, divisible stages) for work and labour done, the innocent party may sue either for damages for breach of contract or, at the innocent party’s option, for restitution in respect of the value of services rendered under the contract.”
“The decisions of the House of Lords in Johnson v. Agnew,[1980] AC 3677 , Photo Products v. Securicor Transport,[1980] AC 827 and Lep Air Services Ltd v. Rolloswin Investments Ltd,[1973] AC 331 establish the position where there is a repudiation of the contract which is accepted or which is effective to bring the contract to an end. In those circumstances the contract is not rescinded ab initio, but future obligations are discharged from the moment the contract comes to an end. All accrued rights remain in being and, so far as executory elements are concerned, the primary obligation is replaced by a secondary obligation to pay damages.”
“This excludes not only an implied contractual term but a claim in unjust enrichment.”
“[133] . . . where the basis of the consideration is expressly and unconditionally spelt out on the face of a valid and subsisting contract, as here, there is no proper scope for inquiring into an alternative basis that is plainly contrary to the express basis freely agreed between the parties. . . .”