Disk locks

[SRS]

Yes, that's true. I really meant when parking your bike in a public place, where you can't hear it yourself.

My house is surrounded by CCTv cameras with big arrays of red-glowing LEDs that shine like ray-guns. I think they tend to put off would-be thieves.

Public places, I understand. Alarms are a waste of space.

I saw one Youtube video, a guy with safety goggles and a cordless disk cutter. Central London, loads of people, not one person questions his actions.

People really do not want to get involved.
Cameras, as you say can be an effective deterrent.