I'm in awe of these guys. C4 showed a documentary called 'Jump London' a couple of years ago featuring Foucan and his mates, amazin stuff in the Capital including HMS Belfast and The Royal Albert Hall. There's a Youtube clip
here but I'd recommend you see the full prog if you can (available on dvd).
As a young lad in the 70's, I used to do something vaguely similar, running along neighbours garden walls, but nowhere near as athletic and elegant as parkour