Bloomsbury, 12 March 2015

Pb, 368 pp

Kim Philby was the most notorious British defector and Soviet mole in history. Agent, double agent, traitor and enigma, he betrayed every secret of Allied operations to the Russians in the early years of the Cold War.

Philby's two closest friends in the intelligence world, Nicholas Elliott of MI6 and James Jesus Angleton, the CIA intelligence chief, thought they knew Philby better than anyone, and then discovered they had not known him at all. This is a story of intimate duplicity; of loyalty, trust and treachery, class and conscience; of an ideological battle waged by men with cut-glass accents and well-made suits in the comfortable clubs and restaurants of London and Washington; of male friendships forged, and then systematically betrayed.

With access to newly released MI5 files and previously unseen family papers, and with the cooperation of former officers of MI6 and the CIA, this definitive biography unlocks what is perhaps the last great secret of the Cold War.

It reads like fiction, which is testament to the extraordinary power of the story itself but also to the skills of the storyteller . at least as compelling as any of the great fictionalised accounts of Britain's greatest traitor and one of the best real-life spy stories one is ever likely to read ***** ( Daily Express )

Illuminating, gripping and moving . What Macintyre reveals - but not too quickly - is the extent to which those who confided in him, as friends or colleagues or both, were made unwitting accessories to treason ( Evening Standard )