The message
from "nightjar" cpb@insert my surname here.me.uk contains these words:

When the driving test theory test was introduced, one of the national
newspapers commissioned a poll of drivers. IIRC, the least recognised signs
was the minimum sped limit, but the priority signs you mention were not far
behind.

I don't think I have ever seen a minimum speed limit sign. Are there any
at all in the UK?

--
Roger Chapman