Just looked the highway code for stopping distances.
Speed is in mph
Stopping distances in metres
Or in "car lengths"
that only came in in the early 90s, as I remember I was learning to drive, and had all the stopping distances/thinking distances memorised in feet, and then my driving instructor mentioned in passing in my last lesson before my test, oh theres a new highway code, the distances are in metres now and you might get asked for both !!!
cue panic, off to a bookshop to find the newest highway code to buy and tried to memorise them in metres, fortunately they only asked for them in feet.