Why does corned beef come in odd-shaped tins and with a key for opening it? – M.

Corned beef tins were issued to soldiers during the First World War.

The tin is a tapered trapezoidal, and it’s thought that was because round tins took up too much room in a soldier’s kit bag, and square tins would need a tin opener, hence the key.

Why they remain like this is, I’m afraid, a mystery to me.