At a branch of downmarket discount retailers B&M recently, I asked the cashier if I could make some change for a trolley. He handed me a sardine-can key and asked if I knew how to use it.

That jimmying the coin operated locking mechanism with part of a tin of fish is considered semi-common knowledge leads me to suspect Britain's trolly theft problem is endemic!

I've also bought a tin of sardines. Just in case.