Re Casey's Patents

Applying the first limb of the test to the facts, the court found no difficulty in concluding that Casey's services had been rendered at the request of the patent owners. The owners had specifically asked Casey to act as the practical manager in promoting and working the patents. This was not a case of a volunteer who had thrust services upon the owners uninvited and then sought payment after the fact. Casey's engagement was the direct result of a request, and that request provided the essential foundation for the exception to operate.

On the second limb, the court held that the circumstances plainly carried a mutual understanding that Casey's services would be remunerated. The nature of the services — managing the practical working of commercial patents — was not of a kind that would ordinarily be performed gratuitously. A reasonable person in Casey's position, performing valuable commercial services at the owners' request, would understand that those services were to be paid for, and the owners, by requesting such services, implicitly acknowledged the same. The absence of a fixed figure for remuneration at the outset did not negate the existence of this mutual understanding; it merely left the quantum to be determined subsequently.

The third limb — that a promise made at the time of performance would have been enforceable — was also satisfied on the facts. Had the owners promised Casey a share of the patents at the moment they requested his services, that promise, supported by Casey's agreement to render those services in return, would have constituted a straightforwardly enforceable contract. There was no vitiating factor that would have prevented such a contract from arising. The promise in the letter was accordingly not the creation of a new obligation from nothing, but the express confirmation and quantification of an obligation that had been implicitly undertaken from the beginning of the arrangement.

The court therefore approached the transaction as a continuous and coherent whole rather than as two wholly distinct episodes — the performance of services followed by an independent and gratuitous promise. The request by the owners, Casey's performance of the requested services under an implied understanding that he would be remunerated, and the subsequent promise fixing the one-third share together constituted a single transaction from which a binding contractual obligation arose. The promise in the letter was the final and express step in a process that had been set in motion at the moment the owners requested Casey's services.

The court also addressed the argument that the promise was unenforceable because it was a promise to transfer an existing asset — the one-third share of the patents — rather than a promise to pay money. This argument was rejected. The form of the remuneration is irrelevant to the question of whether the promise is supported by consideration. What matters is whether the promise was made in circumstances satisfying the three-part test. The transfer of a proprietary interest in the patents was equally capable of constituting valid remuneration for services rendered as a promise to pay a sum of money would have been.

Importantly, the court distinguished the situation before it from the paradigm case of bare past consideration, in which a promisor, wholly voluntarily and without any prior request, decides to reward someone for an act already completely performed without any prior arrangement or mutual understanding. In such cases, the past consideration rule applies in its full rigour because the subsequent promise is truly a gift dressed up in the language of contract, and the act referred to as consideration has no real connection to the promise. In the present case, by contrast, the prior services were requested, were performed under an implied understanding of payment, and were precisely the subject-matter of the subsequent promise. The past consideration rule is therefore inapplicable.

The Court of Appeal held that the promise made by the patent owners to give Casey a one-third share of the patents was enforceable. Past consideration is capable of constituting valid consideration to support a subsequent promise where: the act was performed at the request of the promisor; the circumstances were such that the parties mutually understood that the act would be remunerated; and a promise to pay made at the time of performance would have been legally enforceable.

On the facts, all three conditions were satisfied. Casey's services had been rendered at the express request of the patent owners, in circumstances carrying a clear mutual understanding that those services would be paid for, and there was no obstacle to enforcement of a contemporaneous promise. The subsequent promise to give Casey a one-third share of the patents therefore represented the quantification and completion of an obligation already impliedly undertaken at the time the services were requested, and was accordingly binding upon the owners.

Re Casey's Patents occupies a central position in the English law of contract as the leading modern authority for the proposition that past consideration can, in defined circumstances, support an enforceable promise. The case is significant not merely for confirming the exception recognised in Lampleigh v Brathwait (1615) Hob 105 but for articulating that exception in a clear and systematic three-part test. The formulation associated with Bowen LJ has been repeatedly cited in subsequent case law and in every major English contract law textbook as the authoritative statement of when the past consideration rule does not apply.

The practical significance of the case is considerable, particularly in commercial and employment contexts. It is common for remuneration to be formally agreed or quantified only after services have been performed or partially performed. Without the exception confirmed in Re Casey's Patents, an employer or principal who delayed in fixing the terms of payment could escape liability on the ground that any promise made after performance was unsupported by consideration. The case ensures that such arrangements are not rendered unenforceable merely because the precise quantum of remuneration was left to be determined retrospectively.

The principle has been applied and affirmed in subsequent English authorities. In Pao On v Lau Yiu Long [1980] AC 614, the Privy Council endorsed the three-part test from Re Casey's Patents and confirmed that it represents the correct approach to past consideration under English law. Lord Scarman, delivering the advice of the Board, expressly approved Bowen LJ's formulation, thereby cementing its status as the authoritative test and extending its application beyond purely domestic English cases to the broader common law world.

The case also serves as an important illustration of the courts' broader approach to consideration doctrine: rather than applying rules mechanically in ways that produce commercially absurd results, the courts look to the substance and structure of the transaction as a whole. The conceptual technique of treating the initial request, the subsequent performance, and the later promise as constituents of a single continuous transaction reflects a pragmatic and commercially sensitive approach to contract formation that continues to influence how consideration is analysed in complex or multi-stage dealings.