accident in supermarket car park

[ranjen]

A couple of weeks ago I witnessed along with about 13 other cars a car backing out of a car spot, he was a driver of around 58 - 60ish, because there was a line of traffic behind him he was not able to reverse back in a straight line, most sensible people would have waited, he proceeded to turn the vehicle crashing into the vehicle behind him and leaving an awful scratch up the side of it, but even when he realised his car was getting closer and closer to the car next to him he still proceeded to complete his manoeuvre regardless of the damage, I managed to get his registration number but failed to obtain the numer of the car he damaged.  This driver did not stop, he did not seem at all flustered and he drove off as if it what had just taken place happened every minute of the day - I was late for a meeting and could not stop at the time.  What should I do? I have his registration number.