291. Estoppel.

A person entitled to a charge over or an interest in property who has, knowingly or unknowingly, allowed or encouraged a subsequent incumbrancer to assume to his detriment that his security has priority may be estopped from asserting priority if it would be unconscionable for him to do so1. Thus a mortgagee will be postponed if he has returned the deeds to, or left them with, the mortgagor for the purposes of enabling the mortgagor to raise money on them, notwithstanding that the limit which he has assigned for the loan has been exceeded