The Cambridge Five

Background

In the early 1930s a group of young men associated with the University of Cambridge — Cambridge in this period being a particularly intense political-intellectual environment, with the Marxist economist John Maynard Keynes, the philosopher Ludwig Wittgenstein, and a substantial body of left-leaning students and scholars all in residence — were progressively recruited into work for Soviet intelligence. The recruiters were officers of the OGPU and its successor service the NKVD, working through the Soviet illegal-resident apparatus in London and Western Europe.¹

The five men whose identification as Soviet agents has produced the canonical "Cambridge Five" account were Harold "Kim" Philby (1912–1988), Donald Maclean (1913–1983), Guy Burgess (1911–1963), Anthony Blunt (1907–1983), and John Cairncross (1913–1995). All were students or fellows at Cambridge in the early 1930s; Maclean and Burgess at Trinity Hall and Trinity College respectively, Philby at Trinity College, Blunt as a Fellow of Trinity, and Cairncross at Trinity. Their political alignment with Marxism — variously through the period in which the Soviet Union appeared to many British intellectuals as the only credible counter-force to Nazi Germany — was the basis for Soviet recruitment.²

The recruitments were principally the work of the Soviet illegal residents Arnold Deutsch, Theodore Maly, and successive Soviet officers operating in London during the 1930s. The recruitments followed a deliberate Soviet strategy of identifying promising young students whose political convictions could be channelled into long-term penetration of British state institutions; the strategy contrasted with the more typical pattern of recruiting already-positioned officials. The Five were recruited not for immediate operational use but for long-term penetration in positions to which they would rise across subsequent decades.³

The Operation

The Five took up positions in British state institutions across the late 1930s and 1940s. Philby joined the Secret Intelligence Service in 1940 and rose through wartime postings — including a period in Iberia and Section V of the Service — to become head of the anti-Soviet section by 1944. Maclean joined the Foreign Office and rose through diplomatic postings in Paris and Washington, where he served as First Secretary at the British Embassy and had access to substantial Anglo-American material on the post-war atomic-energy programme. Burgess held various Foreign Office, BBC, and intelligence-adjacent positions, including a period in the Foreign Office's News Department. Blunt served in the Security Service (MI5) during the Second World War; subsequently he held the position of Surveyor of the King's (later Queen's) Pictures from 1945. Cairncross served at the Foreign Office, the Treasury, the Government Code and Cypher School at Bletchley Park, and the Secret Intelligence Service.⁴

Across the 1940s and into the early 1950s the Five transmitted to Soviet intelligence a substantial volume of material. Philby provided detailed material on SIS operations against the Soviet Union, including the wartime Anglo-American agreement on signals-intelligence cooperation that became the UKUSA arrangement, and post-war SIS attempts to insert agents into the Baltic states and the Soviet Union itself — operations that produced the deaths of substantial numbers of inserted agents through Philby's compromise of operational details. Maclean provided material on Anglo-American atomic-energy cooperation. Cairncross, while at Bletchley Park, provided material on German cryptographic work that Soviet sources used in their own operations. Blunt, from his Security Service position, provided material on counter-intelligence priorities and operations. Burgess provided material across his various postings.⁵

The substantive intelligence-historical effect was substantial. Philby alone — rising to a position from which he was widely expected to succeed Sir Stewart Menzies as Chief of the Service ("C") — represented the most consequential single foreign penetration of any Western intelligence service in the twentieth century.⁶

Disclosure

The unravelling of the Five proceeded across a fifteen-year period. The first serious counter-intelligence concerns came from the Anglo-American VENONA programme — the joint US-UK signals-intelligence work to decrypt Soviet diplomatic and intelligence communications intercepted during the 1940s. VENONA decrypts in 1948–1949 identified that a Soviet agent codenamed HOMER had been operating in the British Embassy in Washington; investigation progressively narrowed the suspect pool to Maclean.⁷

In May 1951 — alerted by Philby that Maclean was about to be questioned by MI5 — Burgess and Maclean fled to the Soviet Union. The defection produced the most consequential British intelligence crisis of the post-war period. Philby, who was at this time the SIS liaison to the FBI in Washington, was recalled to London for questioning. The investigation produced no admissible evidence sufficient for prosecution; Philby was retired from the Service with a pension and lived in Beirut as a journalist for the Observer and the Economist until his own defection to Moscow in January 1963, alerted that British intelligence had now obtained admissible evidence against him through the testimony of an old Cambridge contemporary.⁸

Blunt was identified by MI5 in 1963 through the testimony of an American whom he had attempted to recruit during the 1930s. Blunt confessed in exchange for immunity from prosecution and continued in his position as Surveyor of the Queen's Pictures until 1972, with a knighthood (KCVO) granted to him in 1956. The confession was held secret until November 1979, when the journalist Andrew Boyle's book The Climate of Treason triggered Prime Minister Margaret Thatcher's announcement to the House of Commons that Blunt had been a Soviet agent. Blunt's knighthood was annulled.⁹

Cairncross was the last of the Five to be publicly identified, partly confessing to MI5 in 1964 but his identification as a Soviet agent — and as the "Fifth Man" of the Cambridge group — being formally confirmed only in 1990, with the publication of Yuri Modin's memoir My Five Cambridge Friends and Cairncross's own posthumous statement.¹⁰

Legacy

The Cambridge Five case has remained, for more than seven decades, the load-bearing reference case for the institutional capacity of intelligence services to be penetrated by determined and patient foreign services. Successive British inquiries — the post-1951 Cadogan and Manchester reviews, the post-1963 Roger Hollis era reviews of the Service's counter-intelligence work, and successive academic reconstructions — have produced extensive analysis. The Service's response to the case shaped the post-1956 institutional culture and counter-intelligence practice; the consequences for recruitment, training, and security clearance procedures across British intelligence were substantial.¹¹

For the broader question of Western counter-intelligence the case has been the subject of substantial academic and policy literature, including Christopher Andrew's authorised history of MI5, The Defence of the Realm (2009); Keith Jeffery's authorised SIS history MI6: The History of the Secret Intelligence Service 1909–1949 (2010, covering the period to Philby's mid-Service career); Christopher Andrew and Vasili Mitrokhin's The Sword and the Shield (1999); and Ben Macintyre's A Spy Among Friends: Kim Philby and the Great Betrayal (2014). Mitrokhin's archival material, brought to the United Kingdom in 1992 from Soviet Foreign Intelligence Service (SVR) records, provided the principal late-Soviet/post-Soviet documentation.¹²

The case has also functioned as a reference for the broader cultural-political question of motivation: how a particular cohort of ostensibly privileged young Englishmen came to commit themselves to the Soviet Union across decades, and how the institutional culture of mid-twentieth-century British intelligence shaped their continued presence in the Service across years of accumulating evidence.¹³

Related agencies

This dossier relates directly to the Secret Intelligence Service, where Philby served, and the Security Service, where Blunt served and which conducted the principal counter-intelligence investigations. The Soviet historical context relates to the predecessor institutions of what is now the Foreign Intelligence Service — the KGB First Chief Directorate, which inherited NKVD foreign-intelligence operations including the Cambridge Five reporting. The country-level context is on the pages for the United Kingdom and Russia.

Sources & Further Reading

1. Christopher Andrew and Oleg Gordievsky, KGB: The Inside Story (HarperCollins, 1990); Christopher Andrew and Vasili Mitrokhin, The Sword and the Shield: The Mitrokhin Archive and the Secret History of the KGB (Basic Books, 1999).
2. Robert Cecil, A Divided Life: A Personal Portrait of the Spy Donald Maclean (Bodley Head, 1988); Andrew Lownie, Stalin's Englishman: The Lives of Guy Burgess (Hodder & Stoughton, 2015).
3. Andrew and Mitrokhin, The Sword and the Shield; Yuri Modin, My Five Cambridge Friends (Farrar Straus Giroux, 1994).
4. Ben Macintyre, A Spy Among Friends: Kim Philby and the Great Betrayal (Crown, 2014); Stephen Dorril, MI6: Inside the Covert World of Her Majesty's Secret Intelligence Service (Free Press, 2000).
5. Andrew, The Defence of the Realm: The Authorized History of MI5 (Allen Lane, 2009); Andrew and Mitrokhin, The Sword and the Shield.
6. Macintyre, A Spy Among Friends; Phillip Knightley, The Master Spy: The Story of Kim Philby (Knopf, 1989).
7. Robert Louis Benson and Michael Warner (eds.), Venona: Soviet Espionage and the American Response, 1939–1957 (NSA / CIA, 1996); Christopher Andrew, For the President's Eyes Only: Secret Intelligence and the American Presidency from Washington to Bush (HarperCollins, 1995).
8. Macintyre, A Spy Among Friends; Knightley, The Master Spy.
9. Andrew Boyle, The Climate of Treason: Five Who Spied for Russia (Hutchinson, 1979); Statement of Prime Minister Margaret Thatcher to the House of Commons, 15 November 1979, Hansard HC Deb 15 November 1979 vol 973; Miranda Carter, Anthony Blunt: His Lives (Macmillan, 2001).
10. Modin, My Five Cambridge Friends; John Cairncross, The Enigma Spy: An Autobiography (Century, 1997).
11. UK National Archives, KV 2 series — declassified MI5 personal files including Philby, Burgess, Maclean; Andrew, The Defence of the Realm; Keith Jeffery, MI6: The History of the Secret Intelligence Service, 1909–1949 (Bloomsbury, 2010).
12. Andrew and Mitrokhin, The Sword and the Shield, op. cit.
13. John Le Carré, The Pigeon Tunnel: Stories from My Life (Viking, 2016), sections on the Cambridge Five and intelligence-cultural questions; Verne W. Newton, The Cambridge Spies: The Untold Story of Maclean, Philby, and Burgess in America (Madison Books, 1991).