In Treachery, noted intelligence authority Chapman Pincher makes a compelling case that Roger Hollis, head of MI5 from 1956 to 1965, was himself a double agent, acting to undermine and imperil the UK and America. Myriad intriguing case histories are portrayed, including that of Lt Igor Gouzenko, a Red Army cipher clerk whose 1945 disclosure of a mole in MI5 touched off the Cold War. With a mass of new evidence, some from Russian sources, Pincher also provides exciting new perspectives on other infamous operatives, including Kim Philby and Klaus Fuchs. Perhaps most explosively, Pincher posits that long after Hollis stepped down, a cover-up was perpetrated at the highest levels, even involving Margaret Thatcher, to conceal the truth for ever - a deception that continues today. Treachery warns us to protect our society and institutions from enemy infiltration in the future. It is a revelatory work that puts twentieth-century politics and war into stunning new relief.