Glorious and nostalgic: how to make corned beef pie

A few weeks ago I was at the super-market juggling a toddler, several heavy bags and, it transpired, no pound coin to insert into a trolley. A kind employee came to my rescue: on her key ring was one of those little keys you use to open tins of corned beef, which she deftly inserted and released, and lo, the trolley was mine.