Revenue and Customs Commissioners v Benchdollar Ltd

Estoppel by convention based on a common assumption requires that the assumption be expressly shared and 'crossed the line' between the parties, that the party to be estopped have assumed some responsibility for it by conveying an expectation of reliance, and that the party asserting the estoppel have in fact relied on the common assumption to a sufficient degree to render it unjust to allow the other to resile.