Williams v Roffey Bros & Nicholls (Contractors) Ltd
Williams v Roffey Bros & Nicholls (Contractors) Ltd [1989] EWCA Civ 5 is a leading English contract law case. It decided that in varying a contract, a promise to perform a pre-existing contractual obligation will constitute good consideration so long as a benefit is conferred upon the 'promisor'.
Source: Wikipedia — Williams v Roffey Bros & Nicholls (Contractors) Ltd (CC BY-SA 4.0)