CCTV - wrong method, wrong purpose?

I'm no great fan of CCTV. But neither am I a great fan of sloppy reporting or sloppy debate. We are told that CCTV cameras are an expensive waste of time because they don't help solve crime - except in one case per thousand cameras.

There are two things wrong with this analysis, if I can call it that. The first is that the evidence reported suggests it's not the cameras themselves that are failing, but the way they're being used. If the cameras don't take pictures, as is reported, and if they're being examined by untrained people (though I suppose we should be grateful it's being done here, and not outsourced to somewhere like the Philippines or Iowa), it's not surprising that things slip through.

And secondly, solving crime is not the only purpose of CCTV (I assume). Part of the purpose must be the prevention of crime. I have not found anywhere in the current reporting any evidence of whether areas with CCTV suffer less crime. In fact I don't know of any statistical evidence about this, so if anyone can point me to some I would be grateful. The only evidence I know of personally is a chat with a town centre car park caretaker one day a few months after cameras were installed in his car park. He said that prior to installation he used to have to sweep up glass from car headlights daily. Since their installation that had ceased to be part of his job because people didn't vandalise car headlights any more. So, has crime in CCTVed areas gone down, or do we have a particularly insouciant class of criminal in this country that continues to commit crime despite the probability of getting themselves recorded doing it?