Peter Wright in 1963 following what Wright refers to as a tip-off by "a fifth man, still inside", he became convinced that the KGB had penetrated the higher reaches of MI5. As claimed in "Spycatcher", Wright had come to believe that Roger Hollis was the highest traitor in MI5. Wright went so far as to begin to make, as he himself put it, "his own 'freelance' inquiries into Hollis' background" shortly before the latter's retirement. According to Wright, his initial, unspecified, suspicion was aroused by his analysis of how a Soviet 'illegal' Lonsdale's arrest in January 1961 was handled by the KGB
Peter Wright Minister Margaret Thatcher in March 1981. Peter Wright, on the basis of his interviews with Sir Dennis Proctor and his friends, also alleged in his book that Proctor, former Permanent Secretary at the UK Ministry of Power, was at the very least, by Proctor's own account, an unwitting source of secret information to the Soviets via his close friend and Soviet spy Guy Burgess, from whom he had kept no secrets which, in Proctor's opinion, obviated the necessity to recruit him. Wright's sights were also focused on Labour prime minister Harold Wilson, suspicions about whom were initially triggered amongst the