27. Estoppel as a limitation on the principles governing the law of mistake.

Where there is no genuine consensus between parties, and therefore prima facie there should be no contract, estoppel may nonetheless have effect to prevent a party from denying that a consensus with the other party exists1. This can apply in relation to mistake as to the parties2, mistake as to the subject matter3, or indeed mistake as to any other terms of a contract4. It is no objection that the estoppel relates to questions of private rights or construction issues5, and it seems that there can be no estoppel as to matters of general law