Soulsbury v Soulsbury [2007] EWCA Civ 969

Facts

• The case concerned a promise made by a deceased husband to his ex-wife, stating she would receive £100,000 if she refrained from enforcing a court order for alimony.
• The ex-wife did not pursue enforcement of the alimony order during the husband's lifetime.
• After the husband's death, the ex-wife sought to enforce the alleged agreement against his estate.
• The Court of Appeal found in her favor, holding that a unilateral contract had been formed through her performance of the requested act.

Issues

1. Whether a unilateral contract is binding and irrevocable once the offeree begins performance of the stipulated act.
2. Whether acceptance of a unilateral contract is effected by the act of performance rather than communication.
3. At what point a unilateral contract is fully formed and enforceable in circumstances where the requested act is refraining from action.

Decision

• The Court of Appeal affirmed that a valid unilateral contract had been formed between the deceased and his ex-wife.
• The court held that the offer could not be revoked once the offeree began performance, following the principle established in previous case law.
• The ex-wife’s inaction—her forbearance from enforcing the alimony order—constituted sufficient performance and acceptance of the offer.
• The contract became fully binding upon the husband's death, at which point the ex-wife had completed the requested performance.

Legal Principles

• In unilateral contracts, acceptance occurs through the performance of the act requested by the offeror, rather than by a communicated agreement.
• The offeror cannot revoke the offer once the offeree has started performance of the requested act.
• Completion (or in some cases commencement) of the requested act fixes the offeror’s liability and makes the contract binding.
• The judgment reaffirms principles from cases such as Errington v Errington and Daulia Ltd v Four Mill Bank Nominees Ltd, emphasizing an implied obligation on the offeror not to prevent performance once it has begun.

Conclusion

Soulsbury v Soulsbury confirms that in unilateral contracts, the offer becomes irrevocable upon commencement of performance and acceptance is effected by performance rather than communication. The contract is enforceable once the stipulated act is completed, providing certainty for offerees acting in reliance on such promises.