'Richard Kerbaj tells a gripping story of Lyalin's role in helping turn the tables in a spying game that the West had been losing.' The Economist'The Defector flows effortlessly from page to page and chapter to chapter. It is genuinely unputdownable; a terrific read.' The Cipher Brief'It looks and reads like a novel . . . all queuing up to lavish praise upon [this] book." James O'Brien'An absolutely thrilling read based on deep research which brings this MI5 asset's importance to life.' Gordon Corera, co-host of The Rest is Classified'Kerbaj is well-placed to recount the facts of this forgotten story . . . one of the most sensational episodes of the Cold War.' Sunday Times'A truly gripping, untold story... The Defector reads like Le Carre but uncovers important truths that are being played out in Putin's Russia today'. Robert Verkaik'Extraordinary' - Hugo Rifkind, TimesRadio'Inspired . . . seamless, and a thrill to read.' The Scotsman'Compelling', Evening Standard'Highly entertaining . . . Certainly the stuff of thrillers.' Sydney Morning Herald'This magnificent book reads like a thriller but it's all true. It has big lessons for today and tomorrow.' The Australian'Reads like a spy novel', ExpressThe Defector is the untold account of how, in 1971, the defection of a KGB saboteur in London led to the expulsion of more than a hundred Soviet 'diplomats' from the UK. Drawing on newly declassified intelligence documents and dozens of interviews with spymasters, The Defector tells a startling story of a Soviet mission to plant fake Kremlin agents within British and American intelligence services, the paranoia that ensued, and how the actions of a genuine turncoat, the former KGB officer Oleg Lyalin, and the secrets he revealed resulted to one of the most dramatic and pivotal moments in the Cold War. Lyalin led MI5 to rethink its relationship with the CIA. And his defection discredited a previous KGB defector, Anatoly Golitsyn, the darling of the CIA, and ultimately destroyed the reputation of the US agency's head of counterintelligence, James Jesus Angleton. As Richard Kerbaj writes: 'There was a poetic irony in Golitsyn's loss of credibility. It came, as he had previously feared, at the hands of a KGB defector. Except Oleg Lyalin had not been sent by the KGB - he was running away from it.'At the heart of Lyalin's story is a narrative entwined with lies, disinformation, Kremlin deception campaigns, intelligence failures by the CIA and MI5, and a tangled love life. Told in full here, for the first time, by one of this country's leading commentators on national security, it reveals how during the darkest moments of the Cold War one of the West's greatest achievements transpired as a result of MI5's break with the CIA. The disclosure of the inside story of this historic event also comes at a time when there is a renewed interest in the relationship between transatlantic spy services - from the intelligence they share or hold back, to the way they respond to their political masters and stand up to threats from Russia.