Back in the 1980s word went around that there was a wonderful new way to pay your mortgage. In those days the process of getting and running a mortgage was almost sacrosanct, and little variation was available. A fairly common route to take was to open an account at the Building Society of your choice, and to put in as much money as you could, the intention being to prove to said Building Society that you were prudent and could be trusted with their money.
When the time for a mortgage arrived, it was best suit on for an appointment with the branch manager to convince him of your dependability, and if you were successful you were given a (typically) 25 year repayment mortgage. Inflation was your friend because you usually started off committed to a monthly repayment which made yours eyes water, but as time went by the real value of this dwindled in significance.
When you had completed your 300 monthly repayments the property was yours. It was all very straightforward until the endowment mortgage arrived. With this you paid only the interest due, with a promise of lower monthly commitment. At the end of the term a sum would be handed to you which would be sufficient...