https://youtu.be/m7vyKZDvUt8?t=22m46s
I started it at the time off set where they describe how they pick a bike. You only need to watch for a couple of minutes. It can help you make your bike less attractive to these people.
My take away is that if you have to park in a theft-ridden city like London, then:
- park near other bikes
- don't have the most expensive/attractive bike there
- cover it
- chain it to a static object
- keep it in public view
Of course, have theft insurance too.