During the Second World War and the early years of the Cold War, at the heart of British intelligence operated one of the most notorious spy networks in history: the Cambridge Five. These were five young men - whose names were Kim Philby, Guy Burgess, Donald Maclean, Anthony Blunt and John Cairncross - who had been recruited in the 1930s by the Soviet secret service, the KGB, while studying at Cambridge University - hence the name "the Cambridge Five". Motivated by a deep disillusionment with the British establishment, despite the fact that they were all part of it, and inspired by the utopia proposed by the writings of Marx and the Soviet Union, the Five managed to penetrate the upper echelons of MI6, the foreign division of the British secret service, also known as SIS (Secret Intelligence Service), the Foreign Office and even the royal court. Kim Philby, undoubtedly the best known of the five, became deputy head of British counter-espionage and was also the official CIA liaison through his contact James Jesus Angleton: for years he passed on vital information to the Soviets, betraying colleagues and friends. The story of Philby's betrayal and the discovery of his betrayal by MI6 was told by Ben Macintyre in his book A Spy Among Friends. Burgess and Maclean were the first to escape to the USSR in 1951, while Philby followed them in 1963 after a daring escape. Blunt, discovered later, confessed in 1964 in exchange for immunity, while Cairncross was only discovered in the 1990s. The Cambridge Five case exposed the vulnerability of the UK and marked the end of an era in which class privilege automatically implied trustworthiness. A small curiosity: one of the MI6 men who were forced to abandon espionage after being "sold out" by Philby was called David John Cornwell, who became a writer under the name of John le Carré: according to many, the plot of Tinker Tailor Soldier Spy, his most famous novel, is a kind of fictionalised biography of Philby's betrayal.