I know it can and has been done by individuals but not during a political demonstration, they can't charge you over ten pounds and as far as I know they can't refuse unless the footage is directly involved in a police investigation. So i was thinking if a large number of none masked up demonstrators were willing to put their names out there and request it we might put a huge strain on the big brother state.

Anyway just a thought.

 http://www.westminster.gov.uk/services/councilgovernmentanddemocracy/dataprotectionandfreedomofinformation/cctv-requesting-footage/