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 MI5 management shortly after his appointment as prime minister in 1964 by James Jesus Angleton, Deputy Director of Operations for Counterintelligence at the CIA. The investigation into Wilson's background by MI5, however, failed to produce any conclusive evidence. When Wright retired in 1976, Harold Wilson was again prime minister. Dame Stella Rimington, MI5 Director General from 1992 to 1996, who was in MI5 while Peter Wright was still working there, wrote in 2001 that she believed that in a Panorama programme in 1988, Peter Wright had retracted his allegation made in his book about the MI5 group of thirty officers