Can there be an unintentional estoppel by convention: the UK Supreme Court (incorrectly) says yes

Abstract

Abstract In a previous article, I discussed estoppel by convention. To summarize, that doctrine permits one person (the “estopper”—usually the plaintiff in a cause of action) from stopping another person (the “estoppee”—often the defendant) from asserting the truth of a fact or the correctness of a principle of law. The point I tried to make was that the estoppel is not nullified simply because the parties knew when entering into the contract or transaction that the fact or principle agreed on was not true; it is because they agreed to proceed on the basis of the convention, not the convention’s veracity, that the estoppel applies. In Tinkler, the United Kingdom Supreme Court held that the estoppel applied. In my respectful view, for the reasons discussed in this article, it erred in doing so.