Was it one of those mini motocross things? was once riding from norbury to streatham and was chatting to a kid on one of them. No lights no license plate, battering down the road, he wanted to know where the nearest petrol station was, I wanted a tow...
Random kid on a motocross bike on the way home, seen no news of anyone being taken out or jewlery stores getting raided so guess it went ok.
https://www.youtube.com/watch?v=bKPFymWuBc8