I mean I know they need to be reported.
But when I had a google earlier it seems that you are meant to call the police when you know they are driving drunk.
I can't do this because I only ever know about it after the fact (neighbour who regularly drives home drunk - I know he's drunk when he gets home and staggers to his door, but I don't ever know in enough time to ring the police so they can actually catch him in the act). I have no idea where he goes so I don't know where he is setting off from either.
Should I just ring (101?) and report his number plate and say I know he does it at least once a week but at random days/times?