Me and a mate "mugged" a bunch of kids for their bikes many years ago.
I say "their" bikes, they'd just stolen a load of track bikes from the lock-ups at Herne Hill velodrome - they were hire bikes and very distinctive. My mate worked at HH at the time and he'd got a call from a local saying he'd seen a bunch about about 6 kids riding these nicked bikes through Dulwich Village. We jumped in the car, headed down there and sure enough they were just exiting Dulwich Park as we drove up.
He braked in front of them and naturally they all fell off. It was quite funny really, none of them could ride the brakeless fixed gear and in trying to ride off pushing a 90+ inch gear they just stalled. We got all the bikes back no probs although one of the scrotes blustered a bit about "calling his Dad", they all just ran off.
Thinking about it, it was very foolish off us. If they'd have actually thought about it, 6 of them could have beaten the shit out of us in no time.