For the aesthetes who graced the Apostles society at Cambridge University in the 1930s, conversion to the communist cause seemed an appropriate reaction to the menace of European fascism. For a few of these young intellectuals, the invitation to spy for the Kremlin was the ultimate proof of loyalty to that cause.

These programmes examine the gradual exposure of the Cambridge Spies and reveal how the names Burgess, Philby, Maclean, Blunt and 'fifth man' Cairncross became synonymous with treachery at the heart of the British establishment.