This chapter discusses ‘equitable estoppel’ raises the question whether such a category even exists. In truth, there are a range of estoppels available both at common law and in equity. A typical situation in which proprietary estoppel claims arise is where promises are made by the absolute owner of land to another person that the other person will acquire an interest in the land if they perform acts that would otherwise be detrimental to them. The cases considered in the subsection demonstrate that proprietary estoppel is a remedial doctrine in that the remedy that the claimant may receive does not necessarily constitute a pre-existing property right. The principal aim of proprietary estoppel is said to be to avoid detriment rather than to enforce the promise. Proprietary estoppel underlines one of the key tenets of equity: that it can do justice between the parties where the ordinary rules of the common law or of statute would have been unfair or unconscionable.