"Roland Perry" wrote

In 1947 it is claimed. But as their first self-service supermarket was
apparently in Maldon in 1956 I'm struggling to understand what separates
a shop from a supermarket (given that in the 60's many so-called
supermarkets were very small with maybe only two tills, like a modern
convenience store).

The story goes that one of the very early self-service shops had a problem.
By the entrance was a pile of baskets with a notice 'Please take a basket.'
It seems that customers did not appreciate that they were supposed to leave
it at the check-out, and not take it home.

Peter