“An equity arises where – (a) the owner of land (O) induces, encourages or allows the claimant (C) to believe that he has or will enjoy some right or benefit over O’s property; (b) in reliance upon this belief, C acts to his detriment to the knowledge of O; and (c) O then seeks to take unconscionable advantage of C by denying him the right or benefit which he expected to receive.”
“…the essential difference between a proprietary estoppel which does not also give rise to a constructive trust, and one that does, is the element of agreement, or at least expression of common understanding, exchanged between the parties, as to the existence, or intended existence, of a proprietary interest, in the latter type of case.”