320. Clog or fetter on the equity of redemption.

On the principle of once a mortgage always a mortgage1, a clog or fetter on the equity of redemption is void2. No agreement between mortgagor and mortgagee contained in the mortgage can make a mortgage irredeemable3. This principle does not apply to debentures issued by a company which can be made irredeemable4, but a forfeiture clause under a lien on fully paid shares may be void as a clog5. No contract between a mortgagor and mortgagee made at the time of the mortgage, and as part of the mortgage transaction or, in other words, as one of the terms