The Cambridge Spy Ring was a ring of spies in the United Kingdom that passed information to the Soviet Union during World War II and was active from the 1930s until at least into the early 1950s. None of the known members was ever prosecuted for spying. The number and membership of the ring emerged slowly, from the 1950s onwards. The general public first became aware of the conspiracy after the sudden flight of Donald Maclean (cryptonym: Homer) and Guy Burgess (cryptonym: Hicks) to the Soviet Union in 1951. Suspicion immediately fell on Harold "Kim" Philby (cryptonyms: Sonny, Stanley), who eventually fled the country in 1963. Following Philby's flight, British intelligence obtained confessions from Anthony Blunt (cryptonyms: Tony, Johnson) and then John Cairncross (cryptonym: Liszt), who have come to be seen as the last two of a group of five. Their involvement was kept secret for many years: until 1979 for Blunt, and 1990 for Cairncross. The moniker Cambridge Four evolved to become the Cambridge Five after Cairncross was added.
The term "Cambridge" refers to the recruitment of the group during their education at the University of Cambridge in the 1930s. Debate surrounds the exact timing of their recruitment by Soviet intelligence. Blunt claimed that they were not recruited as agents until after they had graduated. A Fellow of Trinity College, Blunt was several years older than Burgess, Maclean, and Philby; he acted as a talent-spotter and recruiter.
All of the five were convinced that the Marxism–Leninism of Soviet Communism was the best available political system, and especially the best defence against the rise of fascism. All pursued successful careers in branches of the British government. They passed large amounts of intelligence to the Soviet Union, so much so that the KGB became suspicious that at least some of it was false. Perhaps as important as the intelligence they passed was the demoralizing effect to the British Establishment of their slow unmasking, and the mistrust in British security this caused in the United States.
Many others have also been accused of membership in the Cambridge ring. Blunt and Burgess were both members of the Cambridge Apostles, an exclusive secret society at Cambridge University. Other Apostles accused of having spied for the Soviets include Michael Straight and Guy Liddell.
The following five supplied intelligence to the Soviets under their controller Yuri Modin who later defected to the West. Modin said that Moscow did not really trust the Cambridge double agents during WWII. The KGB had difficulty believing that the men would have access to top secret documents; they were particularly suspicious of Philby, wondering how he could have become an agent given his Communist past. One report later stated that "About half the documents the British spies sent to Moscow were never even read" due to the paranoia. Nonetheless, the Soviets accepted a great deal of secret information, 1,771 documents from Blunt, 4,605 from Burgess, 4,593 from MacLean and 5,832 from Cairncross, during 1941 to 1945.
Donald Maclean and Guy Burgess
Donald Maclean was a British diplomat who was a spy for the Soviet Union during World War II and early on into the Cold War. Maclean studied at the University of Cambridge in the early 1930s where he met Guy Burgess. Burgess was also a British diplomat who spied for the Soviet Union in World War II and early on into the Cold War. They both disagreed with the idea of capitalist democracy. Later they were both recruited by Soviet intelligence operatives and became undercover agents for the Soviet Union. Maclean began delivering information to the Soviet intelligence operatives as a member of the British Foreign Office in 1934. Soon after, Burgess also began supplying information to the Soviet Union in 1936 from his position as a BBC correspondent up until 1938, then as an active member of MI6 intelligence continued to supply classified information up until 1941, and then finally as a member of the British Foreign Office up until 1944.
Maclean and Burgess were soon known as the “hopeless drunks” due to the fact that they had a hard time keeping their secret occupations to themselves. It is said that one time, while highly intoxicated, Burgess risked exposing his second identity. He was leaving a pub where he accidentally dropped one of the secret files he had taken from the Foreign Office. Maclean was also known to have loose lips and said to have leaked information about his secret duties to his brother and close friends. Although they struggled to keep secrets, that did not stop them from delivering information. It is said that Burgess handed over about 389 top secret documents to the KGB within the early part of 1945 along with an additional 168 documents in December of 1949.
All five were active during World War II. Philby, when he was posted in the British embassy in Washington, DC, after the war, learned that US and British intelligence were searching for a British embassy mole (cryptonym Homer) who was passing information to the Soviet Union, relying on material uncovered by the Venona project.
Philby learned one of the suspects was Maclean. Realizing he had to act fast, he ordered Burgess, who was also on the embassy staff and living with Philby, to warn Maclean in England, where he was serving in the Foreign Office headquarters. Burgess was recalled from the United States due to "bad behaviour" and upon reaching London, warned Maclean.
In early summer 1951, Burgess and Maclean made international headlines by disappearing. (They had taken a ship from Southampton to St. Malo, France, a train to Paris, and a flight to Moscow.) Their whereabouts were unclear for some time and the suspicion that they had defected to the Soviet Union turned out to be correct; that did not become public knowledge until 1956 when the two appeared at a press conference in Moscow. A warrant was not issued for their arrest until 1962.
It was obvious they had been tipped off and Philby quickly became the prime suspect, due to his close relations with Burgess. Though Burgess was not supposed to defect at the same time as Maclean, he went along. It has been claimed that the KGB ordered Burgess to go to Moscow. This move damaged Philby's reputation, with many speculating that had it not occurred, Philby could have climbed even higher in the Secret Intelligence Service.
Between 1934 and 1951 MacLean passed numerous secrets to Moscow. The lack of detection was due to the refusal of the Secret Service to listen to warnings from the US, "even after the FBI had established that an agent code-named Homer had been operating inside the British embassy in Washington during the war", according to a review of MacLean's biography (in 2018) by author Roland Philipps.
In 2019, Russia honoured Burgess and Maclean in a ceremony; a plaque was attached to the building where they had lived in the 50s. The head of the SVR foreign intelligence service, praised the duo on social media for "having supplied Soviet intelligence with the most important information for more than 20 years, [making] a significant contribution to the victory over fascism, the protection of our strategic interests and ensuring the safety of our country".
A book review in The Guardian of Andrew Lownie's biography of Guy Burgess included this conclusion: "[leaving] us all the more astonished that such a smelly, scruffy, lying, gabby, promiscuous, drunken slob could penetrate the heart of the establishment without anyone apparently noticing that he was also a Soviet masterspy".
Stalin's Englishman: The Lives of Guy Burgess is a biography of Burgess that argues that he, of all the members of the Cambridge Five, was perhaps the most influential.
Harold "Kim" Philby
Harold "Kim" Philby was a senior officer in Britain’s Secret Intelligence Service, known as MI6, who began his work for the Soviet Union as a spy in 1934. He went on to serve the KGB for 54 years. He was known for passing more than 900 British documents over to the KGB. He served as a double agent.
Investigation of Philby found several suspicious matters but nothing for which he could be prosecuted. Nevertheless, he was forced to resign from MI6. In 1955 he was named in the press, with questions also raised in the House of Commons, as chief suspect for "the Third Man" and he called a press conference to deny the allegation. That same year, Philby was ruled out as a suspect when British Foreign Secretary Harold Macmillan cleared him of all charges.
In the later 1950s, Philby left the secret service and began working as a journalist in the Middle East; both The Economist and The Observer provided his employment there. MI6 then re-employed him at around the same time, to provide reports from that region.
In 1961, defector Anatoliy Golitsyn provided information which pointed to Philby. An MI6 officer and friend of Philby from his earlier MI6 days, John Nicholas Rede Elliott, was sent in 1963 to interview him in Beirut and reported that Philby seemed to know he was coming (indicating the presence of yet another mole). Nonetheless, Philby allegedly confessed to Elliott.
Shortly afterwards, apparently fearing he might be abducted in Lebanon, Philby defected to the Soviet Union under cover of night, aboard a Soviet freighter. For the first seven years in Moscow, he was under virtual house arrest since the Soviets were concerned that he might defect to the West. According to a New York Times article, he was given no rank nor an office. In fact, "for the most part, Philby was frozen out, his suggestions ignored" ... This ruined his life".  After his death, however, Philby was awarded a number of medals by the Soviets.
Anthony Blunt was a former Surveyor of the King's Pictures and later Queen's Pictures for the royal art collection. He served as an MI5 member and supplied secret information to the KGB, while also providing warnings to fellow agents of certain counterintelligence that could potentially endanger them.
In 1964, MI5 received information from the American Michael Whitney Straight pointing to Blunt's espionage; the two had known each other at Cambridge some thirty years before and Blunt had tried to recruit Straight as a spy. Straight, who initially agreed, changed his mind afterwards.
Blunt was interrogated by MI5 and confessed in exchange for immunity from prosecution. As he was—by 1964—without access to classified information, he had secretly been granted immunity by the Attorney General, in exchange for revealing everything he knew. Peter Wright, one of Blunt's interrogators, describes in his book Spycatcher how Blunt was evasive and only made admissions grudgingly, when confronted with the undeniable.
By 1979, Blunt was publicly accused of being a Soviet agent by investigative journalist Andrew Boyle, in his book Climate of Treason. In November 1979, Prime Minister Margaret Thatcher admitted to the House of Commons that Blunt had confessed to being a Soviet spy fifteen years previously.
The term "Five" began to be used in 1961, when KGB defector Anatoliy Golitsyn named Maclean and Burgess as part of a "Ring of Five", with Philby a 'probable' third, alongside two other agents whom he did not know.
Of all the information provided by Golitsyn, the only item that was ever independently confirmed was the Soviet affiliation of John Vassall. Vassall was a relatively low-ranking spy who some researchers[who?] believe may have been sacrificed to protect a more senior one.
At the time of Golitsyn's defection, Philby had already been accused in the press and was living in Beirut, Lebanon, a country with no extradition agreement with Britain. Select members of MI5 and MI6 already knew Philby to be a spy from Venona project decryptions. Golitsyn also provided other information, such as the claim that Harold Wilson (then Prime Minister of the United Kingdom) was a KGB agent.
Golitsyn's reliability remains a controversial subject and as such, there is little certainty of the number of agents he assigned to the Cambridge spy ring. To add to the confusion, when Blunt finally confessed, he named several other people[who?] as having been recruited by him.
Blunt wrote his memoirs but insisted they not be released until 25 years after his death. They were made public by the British Museum in 2009. The manuscript indicated that he regretted having passed information to the Soviets because of the way it eventually affected his life, that he believed that the government would never reveal his treachery and that he had dismissed suicide as "cowardly". Christopher Andrew felt that the regret was shallow, and that he found an "unwillingness to acknowledge the evil he had served in spying for Stalin". 
John Cairncross was known as a British literary scholar until he was later identified as a Soviet atomic spy. He was recruited in 1936 by James Klugmann to become a Soviet spy. He moved to the Treasury in 1938 but transferred once again to the Cabinet office in 1940 where he served as the private secretary of Sir Maurice Hankey, the Chancellor of the Duchy of Lancaster at that time. Four years later, he was transferred to MI6. Following World War II, it is said that Cairncross leaked information regarding the new NATO alliance to the Soviets.
On the basis of the information provided by Golitsyn, speculations raged on for many years as to the identity of the "Fifth Man". The journalistic popularity of this phrase owes something to the unrelated novels The Third Man and The Tenth Man, written by Graham Greene who, coincidentally, worked with Philby and Cairncross during the Second World War.
Cairncross confessed to having been a spy for the Soviets, in a 1964 meeting with MI6 that was kept secret for some years. He was given immunity from prosecution.
The public became aware of his treachery in December 1979, however, when Cairncross made a public confession to journalist Barrie Penrose. The news was widely publicized leading many to surmise that he was in fact the "fifth man"; that was confirmed in 1989 by KGB agent Oleg Gordievsky who had defected to Britain.
Cairncross is not always deemed to have been part of the 'Ring of Five'. Though a student at the University of Cambridge, he only knew Blunt, who was by then teaching modern languages. By 1934, when Cairncross arrived at Cambridge, the other three members of the ring had already graduated.
The most important agent talent spotted by Blunt was the Fifth Man, the Trinity undergraduate John Cairncross. Together with Philby, Burgess, Blunt and Maclean, he is remembered by the Center (Moscow KGB Headquarters) as one of the Magnificent Five, the ablest group of foreign agents in KGB history. Though Cairncross is the last of the five to be publicly identified, he successfully penetrated a greater variety of the corridors of power and intelligence than any of the other four.
This reference suggests the KGB itself recognized Cairncross as the fifth man (found by Gordievsky while doing research on the history of the KGB).
A few sources, however, believe that the "fifth man" was Victor Rothschild, 3rd Baron Rothschild. In his book The Fifth Man, Roland Perry asserts this claim. After the book was published, former KGB controller Yuri Modin denied ever having named Rothschild as "any kind of Soviet agent". Modin's own book's title clarifies the name of all five of the Cambridge spy group: My Five Cambridge Friends: Burgess, Maclean, Philby, Blunt, and Cairncross by Their KGB Controller. Since Rothschild had died prior to publication of the Perry book, the family was unable to start a libel action.
In a 1991 interview with The Mail on Sunday, Cairncross explained how he had forwarded information to Moscow during WWII and boasted that it "helped the Soviets to win that battle (the Battle of Kursk) against the Germans". Cairncross did not view himself as one of the Cambridge Five, insisting that the information he sent to Moscow was not harmful to Britain and that he had remained loyal to his homeland. Unlike many other spies, he was never charged for passing information to Moscow.
For unknown reasons, Prime Minister Alec Douglas-Home was not advised of Anthony Blunt's spying, although the Queen and Home Secretary Henry Brooke were informed. It was only in November 1979 that then-PM Margaret Thatcher formally advised Parliament of Blunt's treachery and the immunity deal that had been arranged 15 years earlier.
A 2015 article in The Guardian discussed "400 top-secret documents which have been released at the National Archives" and indicated that MI5 and MI6 had worked diligently to prevent information about the five from being disclosed, "to the British public and even to the US government". A 2016 review of a new book about Burgess added that "more than 20% of files relating to the spies, most of whom defected more than 50 years ago, remain closed". In conclusion, the review stated that "the Foreign Office, MI6 and MI5 all have an interest in covering up, to protect themselves from huge embarrassment" and that "more taxpayers' money is spent by Whitehall officials in the futile attempt to keep the files under lock and key for ever". 
Under the 30-year rule, the 400 documents should have been made available years earlier. It was particularly surprising that 20 per cent of the information was redacted or not released. A news item as the time stated that "it is clear the full story of the Cambridge Spies has not yet emerged". A summary of the documents indicated that they showed that "inaction and incompetence on the part of the authorities enabled Guy Burgess and Donald Maclean to make their escape to Moscow".
Additional secret files were finally released to the National Archives in 2020. They indicated that the government had intentionally conducted a campaign to keep Kim Philby's spying confidential "to minimise political embarrassment" and prevented the publication of his memoirs according to a report by The Guardian. Nonetheless, the information was publicized in 1967 when Philby granted an interview to journalist Murray Sayle of The Times. Philby confirmed that he had worked for the KGB and that "his purpose in life was to destroy imperialism". This revelation raised concerns that Blunt's spying would also be revealed to the public.
Alleged additional members
Some researchers believe the spy ring had more than five, or different, members. Several of the following have been alleged to be possible Soviet spies:
- Baron Rothschild was named by Roland Perry in his book The Fifth Man. According to Spycatcher, Rothschild had been friendly with Burgess as an undergraduate, and had originally owned the lease on a house off Welbeck Street, No. 5 Bentinck Street, where Blunt and Burgess both lived during the war. This was supposedly confirmed by Yuri Modin, the alleged controller of the five, who—according to Perry—had claimed Cairncross was never part of the group. However in reviewing Perry's book, commentator Sheila Kerr pointed out that as soon as the book came out, Modin denied Perry's version of their discussions (having already stated that the fifth man was Cairncross), and concluded that "Perry's case against Rothschild is unconvincing because of dubious sources and slack methods".
- Leonard Henry (Leo) Long was accused by Blunt in 1964. Blunt claimed to have recruited Long to the Communist cause while Blunt was tutor at Cambridge. Long served as an intelligence officer with MI14 from 1940–45, and later with the British element of the Allied Control Commission in Occupied Germany from 1945–1952. Long passed analyses but not original material relating to the Eastern Front to Blunt. Blunt also was associated with other Cambridge persons subsequently involved in espionage (Michael Straight, Peter Ashby, Brian Symon) but they are generally considered as minor figures as compared to the "Cambridge Five".
- Guy Liddell was an MI5 officer and nearly rose to become director of the service but was passed over because of rumours he was a double agent; he took early retirement from MI5 in 1953 after he was investigated for his personal links to Kim Philby. He was accused of having been the "fifth man" by Goronwy Rees as part of Rees' confession in 1979. The academic consensus is that he was naïve in his friendships rather than a spy.
- Andrew Gow: in his memoirs published in 2012, Brian Sewell suggested that Gow was the 'fifth man' and spy master of the group. This suggestion was subsequently refuted by Anthony Powell.
In popular culture
- Tinker Tailor Soldier Spy (New York 1974). John le Carré's novelisation of his experiences of the revelations in the 1950s and the 1960s which exposed the Cambridge Five traitors.
- A Perfect Spy, by John Le Carré (New York 1986). Events in the life of the character Magnus Pym are partly based upon the life and career of Kim Philby.
- The Untouchable by John Banville. The character Victor Maskell seems to be a combination of Anthony Blunt and poet Louis MacNeice.
- In Alan Moore's graphic novel The League of Extraordinary Gentlemen: Black Dossier, there appears a Cambridge Five analogue consisting of the Famous Five from Greyfriars School, including Harry Wharton who became Big Brother, Bob Kim Cherry (named after Kim Philby) who was also known as Harry Lime and subsequently M or Mother, Francis Alexander Waverly (possibly formerly known as Frank Nugent) and Sir John Night (possibly formerly known as John Bull).
- The Fourth Protocol, a novel by Frederick Forsyth uses a fictionalised Kim Philby as a central character, who conspires to smuggle a portable nuclear weapon into Britain.
- Burgess, Maclean and Philby appear in the Doctor Who Eighth Doctor Adventures novel Endgame dealing with their defection to Russia.
- The Innocent, a novel by Ian McEwan, involves a spy tunnel which the Soviets discover but do not initially expose, similar to the Philby tunnel.
- Philby appears in The Other Woman of the Gabriel Allon series by novelist Daniel Silva
- The plot of Charles Cumming's 2011 novel, The Trinity Six, is built on the premise that there was a sixth spy and that his existence is being covered up by MI6.
- The Hour (BBC TV series)
- Dennis Potter's television play Traitor (1971) is a spy drama television film that features a central character called Adrian Harris (John Le Mesurier) being interviewed in his Moscow flat by western newspaper reporters, eager to get the story on his defection. Harris appears to be a composite of Philby, Burgess and Maclean. Potter later returned to similar territory with Blade on the Feather (1980), inspired by the unmasking of Anthony Blunt, although in this drama the protagonist Jason Cavendish (Donald Pleasence) is clearly modeled after Philby. Philby is later name-checked as the sports reporter on The Daily Telegraph in Potter's Lipstick on Your Collar (1993), and appears to be giving inside tips on horse-races to officials at the War Office.
- The Channel 4 education show KNTV features a character called 'Burgess MacPhilbin', who provides information for teenagers in the form of a spy dossier.
- Philby, Burgess and Maclean, 1977 Granada Television drama-documentary for ITV, re-broadcast on BBC Four in 2007, with Derek Jacobi as Burgess.
- Tinker Tailor Soldier Spy, 1979 miniseries adaptation of John le Carré's novel
- An Englishman Abroad, 1983 dramatization of Burgess in Russia by Alan Bennett
- Blunt: the Fourth Man, 1987 television drama with Anthony Hopkins as Guy Burgess and Ian Richardson as Anthony Blunt.
- Cambridge Spies, 2003 BBC drama with Toby Stephens as Kim Philby, Tom Hollander as Guy Burgess, Rupert Penry-Jones as Donald Maclean, Samuel West as Anthony Blunt, and Alastair Galbraith as John Cairncross.
- Samuel West reprises his role as Anthony Blunt from Cambridge Spies in The Crown in 2019, in the season three episode titled "Olding".
- The Jigsaw Man, 1983 film starring Laurence Olivier and Michael Caine. Caine plays a character named Philip Kimberley who returns to England after his defection.
- Another Country, 1984 adaptation of the play by Julian Mitchell
- A Different Loyalty, 2004 film directed by Marek Kanievska, is inspired by Kim Philby's affair and subsequent marriage to Eleanor Brewer, as well as events leading up to his defection.
- Tinker Tailor Soldier Spy, 2011 adaptation of John le Carré's novel
- The Imitation Game, 2014 biopic of Alan Turing, includes Allen Leech as John Cairncross; Burgess and Maclean are mentioned in passing.
- A Question of Attribution, 1988 dramatization of Blunt's term as Keeper of the Queen's Pictures; and The Old Country 1977 play about a fictional Philby-esque spy in exile, both by Alan Bennett
- Another Country, 1981 play loosely based on Guy Burgess' life by Julian Mitchell
- In 2009, Michael Dobbs wrote a short play, Turning Point, for a series of live broadcast TV plays on Sky Arts channel. Based on a 1938 meeting between a young Guy Burgess and Winston Churchill, the play sees Burgess urging Churchill to fight the appeasement policy of the British government. In the live broadcast, Burgess was played by Benedict Cumberbatch.
- Kim Philby appears as one of the central antagonists in William F. Buckley's 2004 novel Last Call for Blackford Oakes.
- Andrew Sinclair, The Red and the Blue. Intelligence, Treason and the Universities (Coronet Books, Hodder and Stoughten, U.K. 1987) 211 pages ISBN 0-340-41687-4
- "BBC - History - Historic Figures: The Cambridge Spies". www.bbc.co.uk. Retrieved 2021-03-02.
- The fourth man speaks: Last testimony of Anthony Blunt The Independent McSmith, Andy. 23 July 2009.
- "The Spy Game Was a Con Game". Baltimore Sun. 28 November 2014. Retrieved 30 December 2020.
The center concluded that all five must really be British intelligence officers trying to penetrate the KGB.
- "Enigma Anthony Blunt devoted his life to art—and espionage". New Yorker. 6 January 2002. Retrieved 31 December 2020.
- "Guy Burgess | British diplomat and spy". Encyclopedia Britannica. Retrieved 2019-04-19.
- "Cambridge Spies 'hopeless drunks'". 2014-07-07. Retrieved 2019-04-19.
- Turner, Lauren (October 23, 2015). "Cambridge spies: Defection of 'drunken' agents shook US confidence".
- "Notorious spies fled the country through city port". Daily Echo. 20 December 2010. Retrieved 31 December 2020.
Burgess had booked a two-berth cabin on the British Rail ship Falaise
- The Philby Files by Genrikh Borovik, edited by Phillip Knightley, published by Little, Brown and Company, 1994
- "A Spy Named Orphan: The Enigma of Donald Maclean – review". The Guardian. 28 April 2018. Retrieved 30 December 2020.
Donald Maclean: ‘the most quietly productive of the Cambridge spies and perhaps the strangest too’
- "Russia honours two of Britain's 'Cambridge Five' spies". The Guardian. 29 December 2019. Retrieved 30 December 2020.
meticulously researched life of the disreputable but undeniably fascinating Guy, Stalin’s Englishman
- "Guy Burgess: The Spy Who Knew Everyone by Stewart Purvis and Jeff Hulbert – review". The Guardian. 14 September 2016. Retrieved 30 December 2020.
meticulously researched life of the disreputable but undeniably fascinating Guy, Stalin’s Englishman
- Higgins, Andrew (2017-10-01). "Even in Death, the Spy Kim Philby Serves the Kremlin's Purposes". The New York Times. ISSN 0362-4331. Retrieved 2019-04-19.
- Kendrick, M. Gregory (2016). Villainy in Western culture : historical archetypes of danger, disorder and death. Jefferson, NC. ISBN 978-0786498680. OCLC 933590602.
- "Kim Philby and the Age of Paranoia". New York Times. 10 July 1994. Retrieved 1 January 2021.
In fact, Philby's first seven years in the Soviet Union were almost a form of house arrest. Again a victim of deception: "The K.G.B. told him they were afraid the British M.I.6 was going to try to assassinate him, so he had to have guards all the time, close surveillance," Lyubimov said. But the real reason was the Soviets didn't completely trust him not to bolt for home. "They were afraid something would happen. And he would end up back in Britain or even America.""Did he know they didn't trust him?""Oh yes, he knew." "All this time, he wanted to be a hero of this country," Lyubimov says. "But they did everything to prevent him from this." But for the most part, Philby was frozen out, his suggestions ignored. "The K.G.B. was too stupid and impotent to make use of him," Lyubimov reiterated to me. "This destroyed him. This ruined his life."no-break space character in
|quote=at position 289 (help)
- "Moscow square named after notorious British double agent Kim Philby". The Independent. 9 November 2018. Retrieved 1 January 2021.
- "Anthony Blunt | British art historian and spy". Encyclopedia Britannica. Retrieved 2019-04-19.
- "Anthony Blunt memoir reveals spy's regret at 'the biggest mistake of my life'". The Guardian. 24 July 2009. Retrieved 1 January 2021.
- "Memoirs of British Spy Offer No Apology". New York Times. 23 July 2009. Retrieved 1 January 2021.
- "John Cairncross". Atomic Heritage Foundation. Retrieved 2019-04-19.
- "OBITUARIES: John Cairncross". Washington Post. 17 September 2018. Retrieved 22 October 2011.
- "OBITUARIES: John Cairncross". Washington Post. 17 September 2018. Retrieved 22 October 2011.
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- "John Cairncross, Fifth Man in Spy Ring, Dead at 82". Chicago Tribune. 11 October 1991. Retrieved 30 December 2020.
- Smith, Chris (2019). The Last Cambridge Spy: John Cairncross, Bletchley Codebreaker and Soviet Double Agent (1st ed.). Stroud: The History Press. p. 30. ISBN 9780750981477.
- "Rothschild 'spied as the Fifth Man'". The Independent. 22 October 1994. Retrieved 30 December 2020.
Because he was in MI5 they learned things from him. This doesn't make him the fifth man, and he wasn't
- "John Cairncross, Fifth Man in Spy Ring, Dead at 82". AP News. 9 October 1995. Retrieved 30 December 2020.
- "OBITUARIES: John Cairncross". The Independent. 22 October 2011. Retrieved 30 December 2020.
- "PM was not told Anthony Blunt was Soviet spy, archives reveal". The Guardian. 24 July 2019. Retrieved 30 December 2020.
Alec Douglas-Home was kept in the dark about one of the biggest spy scandals of the cold war
- "MI5 and MI6 cover-up of Cambridge spy ring laid bare in archive papers". The Guardian. 23 October 2015. Retrieved 30 December 2020.
- "MI5 and MI6 cover-up of Cambridge spy ring laid bare in archive papers". The Guardian. 6 February 2016. Retrieved 30 December 2020.
- "The silver spoon spy: how Cambridge double-agent Donald Maclean got away with it for so long". History Today. 17 October 2016. Retrieved 1 January 2021.
Newly released evidence on the Cambridge Spies reveals how, among other revelations, inaction and incompetence on the part of the authorities enabled Guy Burgess and Donald Maclean to make their escape to Moscow.
- "Kim Philby: new revelations about spy emerge in secret files". The Guardian. 30 December 2020. Retrieved 30 December 2020.
UK government launched campaign to block memoirs being published fearing damaging disclosures
- A History of MI5 Christopher Andrew 2010
- Abjorensen, Norman. "Following the Moscow Line", in The Sunday Times Canberra, 22 January 1995.[page needed]
- Spycatcher, p. 164.
- Rusbridger, Alan. The Guardian, 10 December 1994.[page needed]
- Sheila Kerr: review of Roland Perry, The Fifth Man, in Loch K. Johnson, Richard C. Thurlow, Gary D. Rawnsley, M. R. D. Foot, J. A. Crang, Pauline Elkes, Andrew Rathmell, Simon Tormey, Sheila Kerr, Len Scott, Mark Ellis, James G. Stewart & Keith Jeffery (1997): Book reviews. Intelligence and National Security, 12(2): 203-228. doi:10.1080/02684529708432424.
- Mrs Margaret Thatcher, The Prime Minister (9 November 1981). "Mr. Leo Long (Written Answers)". Parliamentary Debates (Hansard). House of Commons. col. 40W–42W.
- "Cambridge don was the spy puppet-master, says Brian Sewell". The Times. Retrieved 26 October 2013.
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- Powell, Anthony (2015). Journals, 1982–1986. London: Arrow Books. ISBN 978-1-78475-071-8., pp. 283–284.
- "Philby Burgess & Maclean (1977) | DVD release". Filmuforia. 2015-12-03. Retrieved 2018-06-26.
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- Friday 23 October 2015, The National Archives, File release: Cold War Cambridge spies Burgess and Maclean, nationalarchives.gov.uk