“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.”