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G PS London has the same degree of camera surveillance as you said Germany has. There's a big centre at Kings Cross Station where all the Railway Police have their monitors (of all the Underground entrances) and another one at New Scotland Yard where all the transport police have theirs. The ones in the underground - which are ostensibly just for mass crowd volume monitoring - have an absolutely deadly killer zoom lens that's centrally steerable.
It's *way* overkill for the use it's supposed to be for...
Do the station staff ever use them ? Here in Melbourne, all the underground railway stations have cameras pointing at escalators, up and down the platforms, etc, but if you're doing something silly like riding around on a chair that the ticket guys usually sit upon, you can expect an announcement :) There is also a window that looks into a `monitor' room from a public walkway at one. Oh, and one of the cameras looking up a platform has gum fixed to part of the cover in front of the lens :)