Locks that work

http://www.leisurelakesbikes.com/product/masterlock1000mmintegratedchainlock.aspx?&id=7678

that is my existing lock, will measure the chain thickness tommorrow, the lock barrel itself I would guess is the weakness on this lock. but that said I know nothing of its 'REAL WORLD' attack strength.
For the north, its more than enough for parking up anywhere. But london is different.

In the real world, only take 10-15 second to cut it through with a battery angle grinder.