Equitable Estoppel: Defining the Detriment – A Reply to Denis Ong

Abstract

extract] I have advanced the outlines of an expectation theory of estoppel elsewhere. However, it is a thesis for which I was unable to supply much doctrinal support. The weight of judicial opinion seemed to me to fall clearly on the side of the reliance thesis. But Dr Ong thinks otherwise. According to Ong, the expectation thesis of estoppel finds ample support in the judgment of Dixon J in Grundt v Great Boulder Proprietary Gold Mines Limited. This is venerable authority indeed. It is the locus classicus on the doctrine of estoppel by conduct, both in Australia and in England. But it cannot be conscripted to the cause of the expectation thesis. In the first part of this reply I show that Ong’s reading of Grundt is mistaken. In the second part I criticise his attempt to draw support for the expectation thesis from the law governing equitable relief for breach of contract.