I hope the UK police are more credible than the US ones. I don't think I would believe anything a US cop said about criminal tactics if he was trying to sell some fearmongering.
Not all police lack credibility and whilst there are some in the UK that do I am confident that the officer in question wasn't lying. In my experience he's a fairly upstanding member of society and a cyclist. Also, officers coming to talk about bicycle security on the invite of a local cycling group tend not to be selling fearmongering. The London Metropolitan Police have recently been working in conjunction with cycling groups in the city in an effort to reduce the amount of bike theft going on and increase the amount of bike theft actually reported.
the story about the CCTV and speaking with the arresting officer is hardly 'documented', I wouldn't characterize it as proof either. I'd like to actually see a police report, or even a videotape of an actual theft or something.
Oddly enough the police aren't in the habit of hauling reports and footage around with them, even to cycling groups meeting in community halls. To do could be a potential breach of data protection laws without he proper clearances which are are a little too time consuming and difficult to obtain just for the purposes of showing around to people like some kind of kindergarten show and tell. However it suffices to say that I, and the rest of the people at the meeting, found the officer in question to be reliable and honest.
However, I guess that isn't going to be enough for some people and find this pervasive element of distrust whenever the police are mentioned quite saddening. I wonder how this would have been received if I had lied and said that I had personally witnessed the footage and the arrest report myself.