Until the Police give a sh*t, until the courts take it seriously then NOTHING will happen.
Steal a £2k Rolex and the police will be all over it, steal a £4k bike and the only worry is how to spend the proceeds.
We as cyclists need to be screaming about this we need to make it as much of an issue as road safety.
since the thread title refers to London I presume that you know nothing of the 30 strong bicycle crime unit in London.
According to the Met the Kryptonite New York lock is about the best - it takes a professional thief 22 seconds to get through. Or. as others have suggested, take it with you when you can.