Looking Out for Number One

In my experience: Ask U.K. residents about the baffling little blue and white signs, even now when they've been around for years, and still quite a few will not know that we've actually been not-very-secretly marking our motorways in metric since the 1970s.

The original plan for the M69 in the 1970s, by the way, was for it to be extended south into Warwickshire as a fully-fledged motorway. Warwickshire County Council was on board, according to the trade magazines of the time. Then the government changed.