I reported an attack on someone else a few months ago which sums up a lot of attitudes on this thread.
The cyclist in front of me on the Islington-Hackney LCC backroads route had two bricks thrown at her at point blank range by a gang of pre-teens. She came skidding off and her bike was mangled mess, but the brick hit her on the arm, which swelled up and she was deeply in shock.
Me and another cyclist stopped to help her, at which point the gang returned and tried to intimidate us, saying we were 'disrespecting' them. Anyway, I phoned the cops and an ambulance while I was fixing her bike, and she was all "No, don't bother, it's nothing" until I pointed out that at least in my book it was attempted murder, and secondly she paid her taxes so why shouldn't she ring the cops.
Anyway, after the police admin woman on the phone was useless about finding the street (I was reading it to her off the bloody street sign but she still couldn't spell it/find it on her computer) the pigs turned up after about five minutes and were very sympathetic, but utterly uniniterested in the fact I had five eye-witness descriptions of the kids, who had even returned and presumably live on/around the estate we were in, took no details or notes, and just concluded it was a "rough estate." Which it is, but a simple bit of detective work could probably have netted them an easy conviction.