My dad has one of the old 'freewheeling' Rovers, a 1937 sports saloon.
Basically power is delivered to the back wheels in the same way as a bicycle...
Plus side - clutchless gearchaning (& alleged) better economy
Drawback - no engine braking so it'll run away with you downhill... nice :shake:
oh & you can't engage & disengage the mechanism whilst the vehicle is moving so you have to ride your brakes downhill mmm scary!