14. Proprietary Estoppel

Proprietary estoppel is a doctrine of considerable antiquity, which, while the subject of considerable judicial development in the nineteenth century, lurked in a degree of obscurity until interest in the subject was revived comparatively recently. Estoppel is seen as having two main forms; in land law, it has long been accepted that estoppel can operate directly to found a cause of action. When operating in this way, the doctrine is referred to as proprietary estoppel, which is the focus of this chapter. It first considers the origin of the doctrine before turning to equitable estoppel, estoppel and other concepts, and estoppel and third parties.