The difficulty is setting the priorities for the police. A sting operation involving a lightly secured top of the range bike could, I suspect, take days to get a result - that's days of police time (at least two officers sitting in a van eating doughnuts). CCTV would find it very difficult to identify an individual in the act of stealing a bike (as opposed to lawfully removing the bike next to it) before they have a chance to cycle off in any direction.

I suspect the stopping of motorists on Tower Bridge is either related to crimes that are more regular (i.e. road tax evasion, which the police can spot from number plates and a central database), or for the prevention of terrorism - which is a higher priority in London at the moment than bike theft.

The main method the police use to reduce bike theft is the marking scheme, which they believe does have positive results in reducing crime stats.

If there were a serious spate of bike thefts in a particular area then I would expect the police to be doing more, and their predictive policing models would probably make that happen before I demand such action. When there are a spate of problems (like street drinking and aggressive begging) I do bring this to the attention of the police (via the Safer Neighbourhood Ward Panel) and ask the police to see if they can address the problem.