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
The Black Book of Communism by Joachim Gauck. The introduction was written by Courtois. Historian François Furet was originally slated to write the introduction, but was prevented from doing so by his death. The book has been translated into numerous languages, sold millions of copies and is considered one of the most influential, although one of the most controversial, books written about communism. The book's title was chosen to echo the Jewish Anti-Fascist Committee's "Black Book", a documentary record of Nazi atrocities by Ilya Ehrenburg and Vasily Grossman. In the first chapter of the book entitled "Introduction: The Crimes of Communism", Stéphane Courtois states that