Case Facts
The claimant, a carpenter, entered into a subcontract with the defendant building contractors to carry out carpentry work on a block of 27 flats for an agreed price of £20,000. As the work progressed, the claimant encountered serious financial difficulty because the agreed price was too low for him to operate satisfactorily and at a profit. Consequently, the work fell behind schedule.
The defendants were themselves under a main contract with the building owner, which contained a time penalty clause. Concerned that the claimant would not complete the carpentry work on time and thereby expose them to liability under that penalty clause, the defendants called a meeting with the claimant. On 9 April 1986, the parties reached an oral agreement whereby the defendants promised to pay the claimant an additional sum of £10,300, at the rate of £575 for each flat in which the carpentry work had been completed.
Approximately seven weeks after the oral agreement was reached, the claimant had substantially completed eight more flats. However, the defendants had made only one further payment of £1,500 under the new arrangement. The claimant thereupon ceased work on the remaining flats and brought a claim for the balance owed.
The case was initially heard at Kingston-upon-Thames County Court, where judgment was given for the claimant. The defendants appealed to the Court of Appeal.
Held
The Court of Appeal dismissed the defendants' appeal and upheld the judgment in favour of the claimant.
On the first and principal issue, the court held that where one party to an existing contract promises to make an additional payment to the other in return for that other party's promise to perform his existing contractual obligations, and as a result of making that promise secures a practical benefit or avoids a detriment, the advantage so secured is capable of constituting good consideration for the promise of additional payment. This principle applies provided the additional promise was not extracted by economic duress or fraud.
In applying this principle to the facts, the court identified several practical benefits that had accrued to the defendants by reason of their promise: they ensured that the claimant continued with the work rather than abandoning it in breach of contract; they avoided incurring the financial penalty for delay imposed by the main contract; and they avoided the trouble and expense of engaging substitute contractors to complete the carpentry. The defendants' promise to pay the additional sum resulted in a commercial advantage to them, and that benefit constituted sufficient consideration to support the promise.
On the second issue, the court held that the claimant's substantial completion of eight flats entitled him to be paid the corresponding portion of the £10,300. In the absence of the payment due to him, the claimant had been entitled to cease work on the remaining flats. The court applied the principle from Hoenig v Isaacs [1952] in support of this finding on substantial completion.
Critically, the court distinguished rather than overruled Stilk v Myrick [1809].
Ratio Decidendi
The binding legal principle established is that performance of, or a promise to perform, an existing contractual duty can constitute good consideration for a promise of additional payment, where doing so confers a practical benefit upon the promisor or relieves the promisor of a practical detriment, and where the promise of additional payment was not obtained by economic duress or fraud.
The court's reasoning represented a significant development in the law of consideration. The traditional rule, derived from Stilk v Myrick [1809], held that a promise to do no more than one was already contractually bound to do could not constitute valid consideration. The Court of Appeal in this case did not overrule that authority but distinguished it on the basis that the practical benefit doctrine provides a more nuanced and commercially realistic approach. Where real and tangible benefits flow to the promisor as a result of the re-negotiation — such as the avoidance of delay penalties, retention of a known contractor, and the practical certainty of timely completion — those benefits satisfy the requirement of consideration, even though the promisee is technically undertaking nothing beyond his existing duty.
This approach brought the law closer to commercial reality and recognised that in many genuine re-negotiation scenarios, parties on both sides may derive mutual benefit from a revised arrangement. The court treated the absence of economic duress as a condition of enforceability rather than merely an incidental observation: if the promisor's agreement to pay more was induced by illegitimate pressure, the promise would not be binding regardless of any practical benefit.
The practical benefits identified on the facts — avoidance of the penalty clause under the main contract, continuity of a known subcontractor, and avoidance of the costs of sourcing a replacement — were each individually sufficient to constitute good consideration.
Obiter Dicta
In the course of their judgements, members of the court made observations going beyond the strict ratio. It was noted that the practical benefit doctrine should not be understood as abolishing the existing contractual duty rule altogether. The doctrine operates within defined limits: the promisor must have received a genuine benefit, and the re-negotiation must have been conducted freely and without duress. The court acknowledged the tension between this decision and the broader policy underlying Stilk v Myrick [1809], which was partly motivated by the need to prevent sailors and other workers from holding their employers to ransom in situations of necessity. The court observed that modern commercial law, supported by the developing doctrine of economic duress, is better equipped to police such abuses than a rigid rule denying consideration altogether.
It was also observed that the result in Stilk v Myrick [1809] itself might well have been the same even if the practical benefit doctrine had been available, given the circumstances of that case. The subsequent decision in Re Selectmove Ltd [1995] would go on to demonstrate the limits of the Williams principle by declining to extend it to the analogous situation of a promise to accept part payment of a debt in full satisfaction, where the rule in Foakes v Beer [1884] was held to remain binding authority at Court of Appeal level.