The Secret Intelligence Service (SIS), commonly known as MI6 (Military Intelligence, Section 6), is the British intelligence agency which supplies the British government with foreign intelligence. The SIS Chief is held accountable to the Foreign Secretary. SIS is bound by the Intelligence Services Act 1994. SIS is frequently referred to by the name MI6 (Military Intelligence, Section 6), a name used as a flag of convenience during the First World War when it was known by many names. The existence of the SIS was not officially acknowledged until 1994. It forms a part of the UK’s intelligence machinery alongside GCHQ, MI5 and Defence Intelligence.
In late 2010, the head of the SIS delivered what he said was the first public address by a serving chief of the agency in its then 101-year history. The remarks of Sir John Sawers primarily focused on the relationship between the need for secrecy and the goal of maintaining security within Britain. His remarks acknowledged the tensions caused by secrecy in an era of leaks and pressure for ever-greater disclosure.
History and development
The service derived from the Secret Service Bureau, which was founded in 1909. The Bureau was a joint initiative of the Admiralty and the War Office to control secret intelligence operations in the UK and overseas, particularly concentrating on the activities of the Imperial German government. The bureau was split into naval and army sections which, over time, specialised in foreign espionage and internal counter-espionage activities, respectively. This specialisation was because the Admiralty wanted to know the maritime strength of the Imperial German Navy. This specialisation was formalised before 1914. During the First World War in 1916, the two sections underwent administrative changes so that the foreign section became the Directorate of Military Intelligence Section 6 (MI6), the name by which it is frequently known in popular culture today.
Its first director was Captain Sir George Mansfield Smith-Cumming, who often dropped the Smith in routine communication. He typically signed correspondence with his initial C in green ink. This usage evolved as a code name, and has been adhered to by all subsequent directors of SIS when signing documents to retain anonymity.
First World War
The service’s performance during the First World War was mixed, because it was unable to establish a network in Germany itself. Most of its results came from military and commercial intelligence collected through networks in neutral countries, occupied territories, and Russia.
After the war, resources were significantly reduced but during the 1920s, SIS established a close operational relationship with the diplomatic service. In August 1919, Cumming created the new passport control department, providing diplomatic cover for agents abroad. The post of Passport Control Officer provided operatives with diplomatic immunity.
The debate over the future structure of British Intelligence continued at length after the end of hostilities but Cumming managed to engineer the return of the Service to Foreign Office control. At this time, the organisation was known in Whitehall by a variety of titles including the Foreign Intelligence Service, the Secret Service, MI1(c), the Special Intelligence Service and even C’s organisation. Around 1920, it began increasingly to be referred to as the Secret Intelligence Service (SIS), a title that it has continued to use to the present day and which was enshrined in statute in the Intelligence Services Act 1994.
In the immediate post-war years under Sir George Mansfield Smith-Cumming and throughout most of the 1920s, the SIS was focused on Communism, in particular, Russian Bolshevism. Examples include a thwarted operation to overthrow the Bolshevik government in 1918 by SIS agents Sidney George Reilly and Sir Robert Bruce Lockhart, as well as more orthodox espionage efforts within early Soviet Russia headed by Captain George Hill.
Smith-Cumming died suddenly at his home on 14 June 1923, shortly before he was due to retire, and was replaced as C by Admiral Sir Hugh “Quex” Sinclair. Sinclair created the following sections:
- A central foreign counter-espionage Circulating Section, Section V, to liaise with the Security Service to collate counter-espionage reports from overseas stations.
- An economic intelligence section, Section VII, to deal with trade, industrial and contraband.
- A clandestine radio communications organisation, Section VIII, to communicate with operatives and agents overseas.
- Section N to exploit the contents of foreign diplomatic bags
- Section D to conduct political covert actions and paramilitary operations in time of war. Section D would organise the Home Defence Scheme resistance organisation in the UK and come to be the foundation of the Special Operations Executive (SOE) during the Second World War.
Sinclair died in 1939, after an illness, and was replaced as C by Lt Col. Stewart Menzies (Horse Guards), who had been with the service since the end of World War I.
Second World War
- The cryptanalytic effort undertaken by the Government Code and Cypher School (GC&CS), the bureau responsible for interception and decryption of foreign communications at Bletchley Park.
- The extensive “double-cross” system run by MI5 to feed misleading intelligence to the Germans
- Imagery intelligence activities conducted by the RAF Photographic Reconnaissance Unit (now JARIC, The National Imagery Exploitation Centre).
The chief of SIS, Stewart Menzies insisted on wartime control of codebreaking, and this gave him immense power and influence, which he used judiciously. By distributing the Ultra material collected by the Government Code & Cypher School, for the first time, MI6 became an important branch of the government. Extensive breaches of Nazi Enigma signals gave Menzies and his team enormous insight into Adolf Hitler‘s strategy, and this was kept a closely held secret.
MI6 assisted the Gestapo, the Nazi secret police, via “the exchange of information about Communism”; as late as October 1937, well into the Nazi era, the head of the British agency’s Berlin station, Frank Foley, was still able to describe his relationship with the Gestapo’s so-called communism expert as “cordial”.
The most significant failure of the service during the war was known as the Venlo incident, named for the Dutch town where much of the operation took place. Agents of the German army secret service, the Abwehr, and the counter-espionage section of the Sicherheitsdienst (SD), posed as high-ranking officers involved in a plot to depose Hitler. In a series of meetings between SIS agents and the ‘conspirators’, SS plans to abduct the SIS team were shelved due to the presence of Dutch police. On the night of 8–9 November 1939, a meeting took place without police presence. There, the two SIS agents were duly abducted by the SS.
In 1940, journalist and Soviet agent Kim Philby applied for a vacancy in Section D of SIS, and was vetted by his friend and fellow Soviet agent Guy Burgess. When Section D was absorbed by Special Operations Executive (SOE) in summer of 1940, Philby was appointed as an instructor in the arts of “black propaganda” at the SOE’s training establishment in Beaulieu, Hampshire.
In early 1944 MI6 re-established Section IX, its prewar anti-Soviet section, and Philby took a position there. He was able to alert the NKVD about all British intelligence on the Soviets—including what the American OSS had shared with the British about the Soviets.
Despite these difficulties the service nevertheless conducted substantial and successful operations in both occupied Europe and in the Middle East and Far East where it operated under the cover name Interservice Liaison Department (ISLD).
In August 1945 Russian intelligence officer Konstantin Volkov tried to defect to Britain, offering the names of all Soviet agents working inside British intelligence. Philby received the memo on Volkov’s offer, and alerted the Soviets so they could arrest him. In 1946, SIS absorbed the “rump” remnant of the Special Operations Executive (SOE), dispersing the latter’s personnel and equipment between its operational divisions or “controllerates” and new Directorates for Training and Development and for War Planning. The 1921 arrangement was streamlined with the geographical, operational units redesignated “Production Sections”, sorted regionally under Controllers, all under a Director of Production. The Circulating Sections were renamed “Requirements Sections” and placed under a Directorate of Requirements.
SIS operations against the USSR were extensively compromised by the fact that the post-war Counter-Espionage Section, R5, was headed for two years by an agent working for the Soviet Union, Harold Adrian Russell “Kim” Philby. Although Philby’s damage was mitigated for several years by his transfer as Head of Station in Turkey, he later returned and was the SIS intelligence liaison officer at the Embassy in Washington D.C. In this capacity he compromised a programme of joint US-UK paramilitary operations (Albanian Subversion, Valuable Project) in Enver Hoxha‘s Albania (although it has been shown that these operations were further compromised “on the ground” by poor security discipline among the Albanian émigrés recruited to undertake the operations). Philby was eased out of office and quietly retired in 1953 after the defection of his friends and fellow members of the “Cambridge spy ring” Donald Duart Maclean and Guy Burgess.
SIS suffered further embarrassment when it turned out that an officer involved in both the Vienna and Berlin tunnel operations had been turned as a Soviet agent during internment by the Chinese during the Korean War. This agent, George Blake, returned from his internment to be treated as something of a hero by his contemporaries in “the office”. His security authorisation was restored, and in 1953 he was posted to the Vienna Station where the original Vienna tunnels had been running for years. After compromising these to his Soviet controllers, he was subsequently assigned to the British team involved on Operation Gold, the Berlin tunnel, and which was, consequently, blown from the outset. In 1956, SIS Director John Alexander Sinclair had to resign after the botched affair of the death of Lionel Crabb.
SIS activities included a range of covert political actions, including the overthrow of Mohammed Mossadeq in Iran in the 1953 Iranian coup d’état (in collaboration with the US Central Intelligence Agency).
Despite earlier Soviet penetration, SIS began to recover as a result of improved vetting and security, and a series of successful penetrations. From 1958, SIS had three moles in the PolishUB, the most successful of which was codenamed NODDY. The CIA described the information SIS received from these Poles as “some of the most valuable intelligence ever collected”, and rewarded SIS with $20 million to expand their Polish operation. In 1961 Polish defector Michael Goleniewski exposed George Blake as a Soviet agent. Blake was identified, arrested, tried for espionage and sent to prison. He escaped and was exfiltrated to the USSR in 1966.
Also, in the GRU, they recruited Colonel Oleg Penkovsky. Penkovsky ran for two years as a considerable success, providing several thousand photographed documents, including Red Army rocketry manuals that allowed US National Photographic Interpretation Center (NPIC) analysts to recognise the deployment pattern of Soviet SS4 MRBMs and SS5 IRBMs in Cuba in October 1962. SIS operations against the USSR continued to gain pace through the remainder of the Cold War, arguably peaking with the recruitment in the 1970s of Oleg Gordievskywhom SIS ran for the better part of a decade, then successfully exfiltrated from the USSR across the Finnish border in 1985.
The real scale and impact of SIS activities during the second half of the Cold War remains unknown, however, because the bulk of their most successful targeting operations against Soviet officials were the result of “Third Country” operations recruiting Soviet sources travelling abroad in Asia and Africa. These included the defection to the SIS Tehran Station in 1982 of KGB officer Vladimir Kuzichkin, the son of a senior Politburo member and a member of the KGB’s internal Second Chief Directorate who provided SIS and the British government with warning of the mobilisation of the KGB’s Alpha Force during the 1991 August Coup which briefly toppled Soviet leader Mikhail Gorbachev.
After the Cold War
The end of the Cold War led to a reshuffle of existing priorities. The Soviet Bloc ceased to swallow the lion’s share of operational priorities, although the stability and intentions of a weakened but still nuclear-capable Federal Russia constituted a significant concern. Instead, functional rather than geographical intelligence requirements came to the fore such as counter-proliferation (via the agency’s Production and Targeting, Counter-Proliferation Section) which had been a sphere of activity since the discovery of Pakistani physics students studying nuclear-weapons related subjects in 1974; counter-terrorism (via two joint sections run in collaboration with the Security Service, one for Irish republicanism and one for international terrorism); counter-narcotics and serious crime (originally set up under the Western Hemisphere Controllerate in 1989); and a ‘global issues’ section looking at matters such as the environment and other public welfare issues. In the mid-1990s these were consolidated into a new post of Controller, Global and Functional.
During the transition, then-C Sir Colin McColl embraced a new, albeit limited, policy of openness towards the press and public, with ‘public affairs’ falling into the brief of Director, Counter-Intelligence and Security (renamed Director, Security and Public Affairs). McColl’s policies were part and parcel with a wider ‘open government initiative’ developed from 1993 by the government of John Major. As part of this, SIS operations, and those of the national signals intelligence agency, GCHQ, were placed on a statutory footing through the 1994 Intelligence Services Act. Although the Act provided procedures for Authorisations and Warrants, this essentially enshrined mechanisms that had been in place at least since 1953 (for Authorisations) and 1985 (under the Interception of Communications Act, for warrants). Under this Act, since 1994, SIS and GCHQ activities have been subject to scrutiny by Parliament’s Intelligence and Security Committee.
During the mid-1990s the British intelligence community was subjected to a comprehensive costing review by the government. As part of broader defence cut-backs SIS had its resources cut back 25% across the board and senior management was reduced by 40%. As a consequence of these cuts, the Requirements division (formerly the Circulating Sections of the 1921 Arrangement) were deprived of any representation on the board of directors. At the same time, the Middle East and Africa Controllerates were pared back and amalgamated. According to the findings of Lord Butler of Brockwell’s Review of Weapons of Mass Destruction, the reduction of operational capabilities in the Middle East and of the Requirements division’s ability to challenge the quality of the information the Middle East Controllerate was providing weakened the Joint Intelligence Committee’s estimates of Iraq‘s non-conventional weapons programmes. These weaknesses were major contributors to the UK’s erroneous assessments of Iraq’s ‘weapons of mass destruction’ prior to the 2003 invasion of that country.
War on Terror
During the global war on terror, SIS accepted information from the CIA that was obtained through torture, including the extraordinary rendition program. Craig Murray, a UK ambassador to Uzbekistan, had written several memos critical of the UK’s accepting this information; he was then sacked from his job.
In the run up to the invasion of Iraq in 2003, it is alleged, although not confirmed, that some SIS conducted Operation Mass Appeal which was a campaign to plant stories about Iraq’s WMDs in the media. The operation was exposed in The Sunday Times in December 2003. Claims by former weapons inspector Scott Ritter suggest that similar propaganda campaigns against Iraq date back well into the 1990s. Ritter says that SIS recruited him in 1997 to help with the propaganda effort. “The aim was to convince the public that Iraq was a far greater threat than it actually was.” Towards the end of the invasion, SIS agents operating out of Baghdad international airport with Special Air Service (SAS) protection, began to re-establish a station in Baghdad and began gathering intelligence; in particular on WMDs, after it became clear that Iraq did not possess any WMDs, MI6 had to officially withdraw pre-invasion intelligence about them. In the months after the invasion, they also began gathering political intelligence; predicting what would happen in post-Baathist Iraq. MI6 personnel in the country never exceed 50; in early 2004, apart from supporting Task Force Black in hunting down former senior Ba’athist party members, MI6 also made an effort to target “transnational terrorism”/jihadist network that led to the SAS carrying out Operation Aston in February 2004: They conducted a raid on a house in Baghdad that was part of a ‘jihadist pipeline’ that ran from Iran to Iraq that US and UK intelligence agencies were tracking suspects on – the raid captured members ofPakistan based terrorist group. Shortly before the Second Battle of Fallujah, MI6 personnel visited JSOCs TSF (Temporary Screening Facility) at Balad to question a suspected insurgent, afterwards they raised concern about the poor detention conditions there and as a result the British government informed JSOC in Iraq that prisoners captured by British special forces would only turn them over to JSOC if there was an undertaking not to send them to Balad. In Spring 2005, the SAS detachment operating in Basra and southern Iraq known as Operation Hathor escorted MI6 “case” officers into Basra so they could meet their sources and handlers and MI6 provided information provided that enabled the detachment to carryout surveillance operations. MI6 were also involved in resolving the Basra prison incident; the SIS played a central role in the British withdrawal from Basra in 2007.
In July 2011 it was reported that SIS has closed several of its stations in the past couple of years, particularly in Iraq, where it used to have several outposts in the south of the country in the region of Basra according to the annual report of the parliamentary Intelligence and Security Committee. The closures have allowed the service to focus its attention on Pakistan and Afghanistan, which are its principal stations. On July 12, 2011, MI6 intelligence officers, along with other intelligence agencies tracked 2 British-Afghans to a hotel in Herat, Afghanistan who were discovered to be trying to “establish contact” with the Taliban or al-Qaeda in order to learn bomb-making skills; operators from the SAS arrested captured them and they are believed to be the first Britons to be captured alive in Afghanistan since 2001.
In October 2013, the SIS appealed for reinforcements and extra staff from other intelligence agencies amid growing concern about a terrorist threat from Afghanistan and that the country will become an “intelligence vacuum” after British troops withdraw at the end of 2014.
In March 2016, it was reported that MI6 had been involved in the Libyan Civil War since January of that year, escorted by the SAS, to meet with Libyan officials to discuss the supplying of weapons and training for the Syrian Army and the militias fighting against Islamic State.
In April 2016, it was revealed that MI6 teams with members of the Special Reconnaissance Regiment seconded to them had been deployed to Yemen to train Yemeni forces fighting AQAP, as well as identifying targets for drone strikes.
On 6 May 2004 it was announced that Sir Richard Dearlove was to be replaced as head of the SIS by John Scarlett, former chairman of the Joint Intelligence Committee. Scarlett was an unusually high-profile appointment to the job, and gave evidence at the Hutton Inquiry.
The SIS has been active in the Balkans, playing a vital role in hunting down people wanted by the International War Crimes Tribunal in The Hague. British intelligence operations in the Balkans are thought to have played a vital role in the handover of the former Yugoslav president Slobodan Milošević to The Hague; the SIS has also been heavily involved in the hunt for Radovan Karadžić and General Ratko Mladic, who are linked to a vast range of war crimes including the murder of Srebrenica’s surrendering male population and organising the Siege of Sarajevo.
On 27 September 2004, it was reported that British spies across the Balkans, including a SIS was chief officer in Belgrade and another spy in Sarajevo, were moved or forced to withdraw after they were publicly identified in a number of media reports planted by disgruntled local intelligence services — particularly in Croatia and Serbia. A third individual was branded a British spy in the Balkans and left the office of the High Representative in Bosnia, whilst a further 2 British intelligence officers working in the Zagreb, remained in place despite their cover being blown in the local press. The exposure of the agents across the three capitals has markedly undermined the British intelligence operations in the area, including SIS efforts to capture The Hague’s most wanted men, which riled many local intelligence agencies in the Balkans, some of which are suspected of continuing ties to alleged war criminals. They were riled due to MI6 operating “not so much a spy network as a network of influence within Balkan security services and the media,” said the director of the International Crisis Group in Serbia and Bosnia, which caused some of them to be “upset”. In Serbia, the SIS station chief was forced to leave his post August 2004 after a campaign against him led by country’s DB intelligence agency, where his work investigating the 2003 assassination of the reformist prime minister Zoran Djindjic won him few friends.
On 15 November 2006, SIS allowed an interview with current operations officers for the first time. The interview was on the Colin Murray show on BBC Radio 1. The two officers (one male and one female) had their voices disguised for security reasons. The officers compared their real experience with the fictional portrayal of SIS in the James Bond films. While denying that there ever existed a “licence to kill” and reiterating that SIS operated under British law, the officers confirmed that there is a ‘Q‘-like figure who is head of the technology department, and that their director is referred to as ‘C’. The officers described the lifestyle as quite glamorous and very varied, with plenty of overseas travel and adventure, and described their role primarily as intelligence gatherers, developing relationships with potential sources.
Sir John Sawers became head of the SIS in November 2009, the first outsider to head SIS in more than 40 years. Sawers came from the Diplomatic Service, previously having been the British Permanent Representative to the United Nations.
On 7 June 2011, John Sawers received Romania’s President Traian Băsescu and George-Cristian Malor, the head of the Serviciul Roman de Informatii (SRI) at SIS headquarters.
On 16 November 2011 SIS warned the national transitional council in Benghazi after discovering details of planned strikes, said foreign secretary William Hague. ‘The agencies obtained firm intelligence, were able to warn the NTC of the threat, and the attacks were prevented,’ he said. In a rare speech on the intelligence agencies, he praised the key role played by SIS and GCHQ in bringing Gaddafi’s 42-year dictatorship to an end, describing them as ‘vital assets’ with a ‘fundamental and indispensable role’ in keeping the nation safe. ‘They worked to identify key political figures, develop contacts with the emerging opposition and provide political and military intelligence. ‘Most importantly, they saved lives,’ he said. The speech follows criticism that SIS had been too close to the Libyan regime and was involved in the extraordinary rendition of anti-Gaddafi activists. Mr Hague also defended controversial proposals for secrecy in civil court involving intelligence material.
The Daily Star reported in November 2011 that SIS helped capture Saif al-Islam Gaddafi. The top-secret mission, dubbed Operation X to disguise its purpose, used modern electronic intelligence (ELINT) technologies to bug him along with his friends and family. Gaddafi had been hiding out in the desert for a month but the breakthrough came when he made two phone calls, one after the other, to say he was safe. It allowed the joint British and French bugging operation to pinpoint his location. SIS agents using the £25million top-secret equipment closed in on him before calling in the Libyan snatch squad to apprehend him.
In February 2013 Channel Four News reported on evidence of SIS spying on opponents of the Gaddafi regime and handing the information to the regime in Libya. The files looked at contained “a memorandum of understanding, dating from October 2002, detailing a two-day meeting in Libya between Gaddafi’s external intelligence agency and two senior heads of the SIS and one from MI5 outlining joint plans for “intelligence exchange, counter terrorism and mutual co-operation”.
In February 2015, the Telegraph reported that MI6 contacted their counterparts in the South African intelligence service’s to seek assistance in an effort to recruit a North Korean “asset” to spy on North Korea’s nuclear programme. MI6 had contacted the man who had inside information on North Korea’s nuclear programme, he considered the offer and wanted to arrange another meeting, but a year passed without MI6 hearing from him, which prompted them to request South African assistance when they learnt he would be travelling through South Africa. It is not known whether the North Korean man ever agreed to work for MI6.
Since 1995, SIS headquarters has been at 85 Vauxhall Cross, along the Albert Embankment in Vauxhall on the banks of the River Thames by Vauxhall Bridge, London. Previous headquarters have been Century House, 100 Westminster Bridge Road, Lambeth (1966–95); and 54, Broadway, off Victoria Street, London (1924–66). (Although SIS operated from Broadway, it was actually based at St James’s Street and also made considerable use of the adjoining St Ermin’s Hotel).
The building was designed by Sir Terry Farrell and built by John Laing. The developer Regalian Properties approached the government in 1987 to see if they had any interest in the proposed building. At the same time, MI5 was seeking alternative accommodation and co-location of the two services was studied. In the end this proposal was abandoned due to the lack of buildings of adequate size (existing or proposed) and the security considerations of providing a single target for attacks. In December 1987, Prime Minister Margaret Thatcher‘s government approved the purchase of the new building for the SIS.
The building design was reviewed to incorporate the necessary protection for Britain’s foreign intelligence gathering agency. This includes overall increased security, extensive computer suites, technical areas, bomb blast protection, emergency back-up systems and protection against electronic eavesdropping. While the details and cost of construction have been released, about ten years after the original National Audit Office (NAO) report was written, some of the service’s special requirements remain classified. The NAO report Thames House and Vauxhall Cross has certain details omitted, describing in detail the cost and problems of certain modifications, but not what these are. Rob Humphrey’s London: The Rough Guide suggests one of these omitted modifications is a tunnel beneath the Thames to Whitehall. The NAO put the final cost at £135.05m for site purchase and the basic building, or £152.6m including the service’s special requirements.
The setting of the SIS offices was featured in the James Bond films GoldenEye, The World Is Not Enough, Die Another Day, Skyfall and Spectre. SIS allowed filming of the building itself for the first time in The World is Not Enough for the pre-credits sequence, where a bomb hidden in a briefcase full of money is detonated inside the building. A Daily Telegraph article said that the British government opposed the filming, but this was denied by aForeign Office spokesperson. In Skyfall the building is once again attacked by an explosion, this time by a cyber attack turning on a gas line and igniting the fumes, after which SIS operations are moved to a secret underground facility. In Spectre, the evil head of crime organization Spectre, Ernst Stavro Blofeld, traps Agent 007 James Bond alongside the film’s Bond girl Dr. Madeleine Swann inside the remains of the building. Blofeld then detonated bombs planted in the building, demolishing what was left of the building fully, though Bond managed to save Dr. Swann and escaped before the building exploded.
On the evening of 20 September 2000, the building was attacked using a Russian-built RPG-22 anti-tank rocket. Striking the eighth floor, the missile caused only superficial damage. The Anti-Terrorist branch of the Metropolitan Police attributed responsibility to the Real IRA.
Most other buildings are held or nominally occupied by the Foreign & Commonwealth Office. They include:
- Hanslope Park: on the outskirts of Milton Keynes housing the Her Majesty’s Government Communications Centre, which supports the Foreign & Commonwealth Office and the British intelligence community.
- Fort Monckton: a former fort dating from the 1780s, rebuilt in the 1880s, is now the field operations training centre for SIS.
MI6 is nicknamed The Circus. Some say this was coined by John le Carré (former SIS officer David Cornwell) in his espionage novels. Leo Marks in his autobiographical Between Silk and Cyanide explains that the name arose because a section of Britain’s WWII SOE was housed in a building at 1 Dorset Square, London, which had formerly belonged to the directors of Bertram Mills circus. “This inspired continuity was one of SOE’s favourite in-jokes.”
- 1909–1923: Sir Mansfield Smith-Cumming, KCMG CB
- 1923–1939: Admiral Sir Hugh Sinclair, KCB
- 1939–1952: Major General Sir Stewart Menzies, KCB KCMG DSO MC
- 1953–1956: Sir John Alexander Sinclair, KCMG CB OBE
- 1956–1968: Sir Richard White, KCMG KBE
- 1968–1973: Sir John Rennie, KCMG
- 1973–1978: Sir Maurice Oldfield, GCMG CBE
- 1979–1982: Sir Dick Franks, KCMG
- 1982–1985: Sir Colin Figures, KCMG OBE
- 1985–1989: Sir Christopher Curwen, KCMG
- 1989–1994: Sir Colin McColl, KCMG
- 1994–1999: Sir David Spedding, KCMG CVO OBE
- 1999–2004: Sir Richard Dearlove, KCMG OBE
- 2004–2009: Sir John Scarlett, KCMG OBE
- 2009–2014: Sir John Sawers, KCMG
- 2014–present: Alex Younger, CMG
- List of intelligence agencies
- Cambridge Five, a Cold War Soviet spy ring
- Anthony Blunt (cryptonym: Johnson), MI5 officer and Soviet agent
- Guy Burgess (cryptonym: Hicks), SIS officer and Soviet agent
- John Cairncross (cryptonym: Liszt), SIS officer and Soviet agent
- Donald Maclean (cryptonym: Homer), SIS officer and Soviet agent
- Kim Philby (cryptonym: Stanley), SIS officer and Soviet agent
- James Bond, 007, a fictional character from the popular book, movie and video game franchise, who is said to work for MI6
- David Cornwell (known as John le Carré), author, former SIS officer
- Andrew Fulton, chairman of the Scottish Conservative Party
- Charles Cumming, author
- Paul Dukes, SIS officer and author
- Frederick Forsyth, author and alleged MI5 agent
- Ian Fleming, author of James Bond novels, former NID officer
- Graham Greene, author, former SIS officer
- Ralph Izzard, journalist, author, former NID officer
- Horst Kopkow, SS officer who worked for SIS after the Second World War
- Alec Leamas, fictional SIS (or “the Circus” in the novels) operative in John Le Carré’s Spy Who Came in from the Cold (1963) and portrayed by Richard Burton in the 1965 film
- Sidney Reilly, Ace of Spies, worked for SIS and others
- Alex Rider, fictional agent, unwillingly working for MI6, character in British author Anthony Horowitz’s Alex Rider series
- Alan Blunt, fictional head of Special Operations Division, MI6, character in British author Anthony Horowitz’s Alex Rider series
- Mrs. Jones, fictional deputy head of Special Operations Division, MI6, immediate superior is Alan Blunt
- Ian Rider, fictional agent, uncle of Alex Rider and brother of John Rider
- John Rider, fictional agent, father of Alex Rider and brother of Ian Rider
- Krystyna Skarbek, agent
- Aggie MacKenzie, TV presenter and journalist who spent two years working for MI6
- George Smiley, a fictional character from the popular books of John Le Carré and movie franchise, who works for MI6
- Richard B. Tinsley, SIS officer, station chief during WWI.
- Richard Tomlinson, author, former SIS officer
- Valentine Vivian, Vice-Chief of the SIS and head of counter-espionage, Section V
- Gareth Williams, seconded to SIS from GCHQ, likely to have been unlawfully killed