Promissory Estoppel in UK Law

When the parties to a transaction proceed on the basis of an underlying assumption—either of fact or of law—whether due to misrepresentation or mistake makes no difference—on which they have conducted the dealings between them—neither of them will be allowed to go back on that assumption when it would be unfair or unjust to allow him to do so. If he does seek to go back on it, the courts will give the other such remedy as the equity of the case demands.

Estoppel by convention is not founded on a unilateral representation, but rather on mutually manifest conduct by the parties based on a common, but mistaken, assumption of law or fact: its basis is consensual.

The facts of this case demonstrate that, if (1) a debtor offers to pay part only of the amount he owes; (2) the creditor voluntarily accepts that offer, and (3) in reliance on the creditor's acceptance the debtor pays that part of the amount he owes in full, the creditor will, by virtue of the doctrine of promissory estoppel, be bound to accept that sum in full and final satisfaction of the whole debt.

He suggests at pages 340 to 342 that promissory estoppel is limited to cases where parties are already bound contractually one to the other. It applies whenever representation is made, whether of fact or law, present or future, which is intended to be binding, intended to induce a person to act upon it and he does act upon it. Acting upon it, he has lost any rights against the Supporters Club.

An "estoppel" bars the object of it from asserting some fact or facts, or, sometimes, something that is a mixture of fact and law, that stands in the way of some right claimed by the person entitled to the benefit of the estoppel. The estoppel becomes a "proprietary" estoppel - a sub-species of a "promissory" estoppel - if the right claimed is a proprietary right, usually a right to or over land but, in principle, equally available in relation to chattels or choses in action.

This arises in a situation where a person is entitled to alternative rights inconsistent with one another. If he has knowledge of the facts which give rise in law to these alternative rights and acts in a manner which is consistent only with his having chosen to rely on one of them, the law holds him to his choice even though he was unaware that this would be the legal consequence of what he did.

In my opinion it is a necessary element of proprietary estoppel that the assurances given to the claimant (expressly or impliedly, or, in standing-by cases, tacitly) should relate to identified property owned (or, perhaps, about to be owned) by the defendant. The latter need not be based on an existing legal relationship, but it must relate to identified property (usually land) owned (or, perhaps, about to be owned) by the defendant.