P bought a property from X who had given a mortgage to D. The mortgage had included a term stating that it could not be paid off (and hence the interest redeemed) until the last six weeks of the 21 year lease. HL held that this contradicted the requirement of redeemability of the mortgage.
Lord Macnaghton: “equity will not permit any device or contrivance being part of the mortgage transaction or contemporaneous with it to prevent or impede redemption.”