English Law/Contract/Promissory estoppel

The doctrine of promissory estoppel holds that when one person gives an assurance to another, the other relies on it and it would be inequitable to go back on the assurance, that person will be estopped from doing so: an analogue of the maxim that nobody should profit from their own wrong (nemo auditur propriam turpitudinem allegans). An early example is  in which the Law Lords held that a tenant could not be ejected by the landlord for failing to keep up with contractual repairs because starting negotiations to sell the property gave the tacit assurance that the repair duties were suspended. Similarly, in  Denning J held that a landlord would be estopped from claiming normal rent during World War II because of an earlier assurance that half rent could be paid until end of the war.

Hence, promissory estoppel could circumvent the common law rule of , but is deemed incapable of raising an independent cause of action, so that one party may only plead that another party is estopped from enforcing their strict legal rights as a "shield", but cannot bring a cause of action out of estoppel as a "sword". Yet, where an assurance concerns rights over property, a variant "proprietary estoppel" does allow a claimant to plead estoppel as a cause of action. So in , Mr Crabb was assured he would have the right to an access point to his land by Arun District Council, and relying on that he sold half the property where the only existing access point was. The council was estopped from not doing what they said they would. A number of commentators including P.S. Atiyah, have called for the doctrine of consideration to be abandoned, based on the complex logic used to reach simple decisions, leaving the basic requirements of agreement and an intention to create legal relations. Such a move would also dispense with the need for the common law doctrine of privity.