The London Film Festival was book-ended by thrillers. It opened with The Imitation Game, about Alan Turing's race against time to crack the Enigma code. It closed with Fury, following a WWII tank crew through a series of bloody skirmishes in Germany. But more gripping than either was CITIZENFOUR, which told the story of US whistleblower Ed Snowden as he revealed the US Government's industrial scale spying on its own innocent citizens...