I’ve looked before and couldn’t see it , but I’ve been told on more than one occasion by instructors at Tulliallan that it is a little known piece of legislation, introduced, I think , to exclude things like mopeds , tractors and the like .
I’ve never heard of anyone being prosecuted, and of course if there is a hold up you can’t avoid stopping .
Is that the Police College you're referring to?
Back when I was a teenager in the 80's I applied to go along. The idea was to do a few laps of the skid pan in some old Avenger on bald tyres and then get taken out by proper drivers. The skid pan thing was cancelled because, believe it or not, a contractor had resurfaced it with the wrong tarmac which was way too grippy.
But the drive by the qualified driver was astonishing. At one point I was going "Bloody Scorpio. Rubbish dampers. Bouncing all over the place". Then I looked at the speedo and we were well into treble figures. Racing driver smoothness. Astonishing car control.
Just reading Soldier Spy about the M15 and reading about their driving training reminded me of that little episode.