Promissory estoppel
Promissory estoppel can stop a party going back on a promise — even one unsupported by consideration — where they intended it to be relied upon, the other party did rely on it, and it would be inequitable to let them resile.
Last reviewed 14 June 2026
It originates in Lord Denning's judgment in Central London Property Trust Ltd v High Trees House Ltd [1947] KB 130, building on Hughes v Metropolitan Railway Co. It suspends or modifies existing contractual rights rather than creating new ones.
It is “a shield, not a sword” (Combe v Combe [1951] 2 KB 215): a defence to the enforcement of strict rights, not an independent cause of action, and the reliance must make it inequitable for the promisor to go back on the promise.
Key cases
- Central London Property Trust Ltd v High Trees House Ltd [1947] KB 130
- Hughes v Metropolitan Railway Co (1877) 2 App Cas 439
- Combe v Combe [1951] 2 KB 215
Frequently asked questions
Is promissory estoppel a sword or a shield?
A shield. After Combe v Combe it can only be used as a defence to prevent enforcement of strict legal rights, not as a free-standing cause of action.
Does promissory estoppel require consideration?
No — that is its purpose: it can make a promise binding despite the absence of consideration, where it was relied upon and it would be inequitable to resile.