hotel magnum:
I was told when on the AA the use of the spec required C+E as very few cars were under 750kg and of course were in effect un braked trailers, and only damaged or non runners allowed on the spec, no inter garage moves or deliveries of repaired or bought / sold vehicles.
Which means a non road worthy vehicle can be towed on the road but a road worthy one can’t. 
Seriously they are a pointless dodgy substitute for a decent trailer and winch and they should ban the things.Also think the idea of no trailer heavier than 750 kg allowed to be towed with a 7.5 tonner with just a C1 licence is nuts.Might as well say that someone needs a class 1 to tow a big caravan with a car. 