This four-part series attempts to dramatise the real-life events of four Cambridge students, recruited to spy for the Soviet Union in 1934. The four (Guy Burgess, Anthony Blunt, Kim Philby and Donald Maclean) became career spies, sacrificing any possibility of living a normal life, and in the process disclosing some of the most highly guarded information possessed by British intelligence, including test results from the Atom bomb and the Enigma codes. Impressively played and an intriguing story, but perhaps a little too playful with historical accuracy.