# MI5, MI6, and British intelligence

The British secret state: the 1909 Secret Service Bureau splitting into MI5 and MI6, the Double-Cross and Bletchley in the world wars, the forged Zinoviev Letter, the Cambridge Five's betrayal, the Spycatcher affair and the agencies' avowal and oversight, the 2003 Iraq dossier, post-9/11 rendition complicity, and GCHQ's mass surveillance revealed by Snowden.

*This story parallel: The secret agencies: CIA, FBI, and NSA*
*This story parallel: Special Branch and colonial political policing*
*This story part of: Military and security*
*The Russian oligarchs and the rise of Putin parallel this story*
*Agent provocateurs and false flags parallel this story*
*Northern Ireland: the Troubles and collusion parallel this story*
*Official secrecy: the classification of state knowledge parallel this story*

## 1 October 1909 — Secret Service Bureau founded

The British government set up the Secret Service Bureau to counter German espionage and to run British intelligence gathering abroad. It was a joint Admiralty and War Office body, headed jointly by Captain Vernon Kell and Commander Mansfield Cumming. It is the common ancestor of both MI5 and MI6.

## c. 1 January 1910 — Bureau splits into Home and Foreign Sections

The Secret Service Bureau divided into a Home Section under Vernon Kell, which handled counter-espionage inside Britain and its empire, and a Foreign Section under Mansfield Cumming, which ran agents abroad. The Home Section grew into the Security Service, MI5. The Foreign Section grew into the Secret Intelligence Service, MI6.

## 4 August 1914 — MI5 rounds up German spy network at outbreak of WWI

Within hours of Britain declaring war on Germany, Vernon Kell's Home Section arrested most of a German intelligence network that had been under surveillance since before the war. About twenty agents were rounded up on a single day, crippling German espionage in Britain for the rest of the war. The operation was widely seen as an early success for what would become MI5.

## 1 November 1919 — Government Code and Cypher School founded

The Government Code and Cypher School (GC&CS) was formed by merging the Royal Navy's Room 40 and the War Office's MI1b codebreaking units. It handled British signals intelligence between the wars and through the Second World War. GC&CS is the direct ancestor of GCHQ.

## 25 October 1924 — Zinoviev Letter published

The Daily Mail published a letter purportedly from Soviet official Grigory Zinoviev urging British communists toward insurrection, four days before a general election. The letter was a forgery, and later research pointed to its likely fabrication by White Russian emigres and possible passage through figures with SIS connections. Its publication is widely believed to have damaged the Labour government of Ramsay MacDonald, though historians still debate exactly how it reached the press.

## c. 20 January 1940 — Bletchley Park breaks Enigma traffic

Codebreakers at the Government Code and Cypher School's wartime station, Bletchley Park, achieved their first sustained breaks into German Enigma-encrypted traffic, building on earlier Polish cryptanalytic work. The resulting decrypted intelligence, codenamed Ultra, gave Allied commanders access to German military communications for the rest of the war. Historians credit Ultra with shortening the war, though its full extent stayed classified until the 1970s.

## 2 January 1941 — XX Committee runs the Double-Cross System

MI5 stood up the Twenty (XX) Committee to coordinate the Double-Cross System, under which nearly every German agent sent to Britain was identified, captured, and turned into a double agent feeding false information back to German intelligence. The system fed deception operations through the war, including the D-Day deception plan Fortitude. It is regarded as one of MI5's major wartime successes.

## c. 1 June 1946 — GC&CS becomes GCHQ

After the war the Government Code and Cypher School was renamed the Government Communications Headquarters, GCHQ, and placed under the Foreign Office. It retained the signals intelligence role built up at Bletchley Park, now directed at the emerging Cold War rather than Germany. It moved its main site to Cheltenham in the early 1950s.

## 2 February 1950 — Klaus Fuchs arrested as atomic spy

Physicist Klaus Fuchs, who had worked on the British and American atomic bomb programmes, was arrested after MI5 investigation confirmed he had been passing nuclear weapons secrets to the Soviet Union since the war. He confessed and was convicted, serving nine years in prison. The case exposed serious gaps in wartime vetting of scientists with access to nuclear secrets.

## 25 May 1951 — Burgess and Maclean defect to Moscow

Foreign Office diplomat Donald Maclean, tipped off that he was about to be exposed as a Soviet spy, fled Britain along with fellow diplomat Guy Burgess. Both surfaced in Moscow years later, confirming they had spied for the Soviet Union since the 1930s as part of what became known as the Cambridge Five. Their disappearance triggered a long British mole hunt.

## c. 1 July 1951 — Kim Philby resigns from SIS under suspicion

SIS officer Kim Philby, who had been the British liaison to American intelligence in Washington, was recalled and forced to resign after the Burgess and Maclean defections raised suspicion he had warned Maclean. No charges were brought for lack of proof, and Philby was later publicly cleared by the Foreign Secretary in 1955, allowing him to continue working as a journalist with informal SIS contacts.

## 3 May 1961 — George Blake exposed and convicted

SIS officer George Blake was convicted of spying for the Soviet Union after a defector's tip led to his exposure. He had betrayed British and American agents and operations, including the Berlin Tunnel wiretapping scheme, while working under diplomatic and SIS cover from the early 1950s. He was sentenced to 42 years, the longest determinate sentence handed down by a British court at the time.

## 23 January 1963 — Kim Philby defects to Moscow

Facing fresh evidence and confronted by an SIS colleague in Beirut, Kim Philby fled to the Soviet Union, confirming he had been the senior-most Soviet mole inside British intelligence, dubbed the Third Man. He had spied for the Soviets since being recruited at Cambridge in the 1930s and had reached the rank of a leading SIS counter-intelligence officer. His defection was one of the most damaging breaches in British intelligence history.

## c. 1 April 1964 — Anthony Blunt confesses in secret

Art historian and former MI5 officer Anthony Blunt, by then Surveyor of the Queen's Pictures, confessed privately to having spied for the Soviet Union from the 1930s in exchange for immunity from prosecution. His role as a member of the Cambridge Five was kept secret by the government for fifteen years. He continued in his royal post throughout that period.

## 22 October 1966 — George Blake escapes Wormwood Scrubs

George Blake escaped from Wormwood Scrubs prison with help from anti-nuclear campaigners he had befriended while inside, five years into his 42-year sentence. He made his way to the Soviet Union, where he lived for the rest of his life. The escape was a public embarrassment for the British prison and security establishment.

## 15 November 1979 — Thatcher names Anthony Blunt as the Fourth Man

Prime Minister Margaret Thatcher told the House of Commons that Anthony Blunt had confessed to being a Soviet spy in 1964, publicly confirming his role as the Fourth Man of the Cambridge Five fifteen years after his secret confession. Blunt was stripped of his knighthood. The disclosure came after journalist Andrew Boyle had already identified him in a book, forcing the government's hand.

## 20 July 1985 — MI6 exfiltrates Oleg Gordievsky from Moscow

SIS smuggled its top Soviet asset, KGB colonel Oleg Gordievsky, out of Moscow in the boot of a diplomatic car after he came under suspicion, in an operation codenamed PIMLICO. Gordievsky had been supplying British intelligence with high-level KGB material for over a decade. The operation is regarded as one of MI6's most successful Cold War exfiltrations.

## 13 July 1987 — Spycatcher published after government ban fails

Former MI5 officer Peter Wright published his memoir Spycatcher, alleging extensive MI5 wrongdoing including a claimed plot by rogue officers against Prime Minister Harold Wilson, an allegation Wright made but never proved. The British government's attempt to suppress the book failed in the Australian courts and the House of Lords eventually lifted the UK injunction. The affair exposed internal MI5 disputes to public view for the first time and embarrassed the Thatcher government.

## 18 December 1989 — Security Service Act puts MI5 on a statutory footing

The Security Service Act 1989 gave MI5 statutory recognition for the first time in its eighty-year history, formally avowing its existence and defining its functions in law. It also created a tribunal for complaints against the Service. Before this, the government had never officially acknowledged MI5's existence.

## c. 1 June 1990 — John Cairncross named as the Fifth Man

Journalist and historian accounts drawing on defector Oleg Gordievsky's information publicly identified former civil servant John Cairncross as the Fifth Man of the Cambridge spy ring, following earlier private admissions Cairncross had made to MI5 in the 1960s. Cairncross had passed material from Bletchley Park and other sensitive posts to Moscow during and after the war. He acknowledged passing information to the Soviets but disputed some details of his role.

## c. 1 January 1994 — MI6 moves into Vauxhall Cross headquarters

SIS relocated to its purpose-built headquarters at Vauxhall Cross on the south bank of the Thames, a building whose distinctive appearance became publicly associated with the agency, including in films. The move coincided with the formal statutory avowal of the Service. The building's public visibility marked a shift from decades of official secrecy about MI6's very existence.

## 26 May 1994 — Intelligence Services Act avows SIS and GCHQ

The Intelligence Services Act 1994 gave SIS (MI6) and GCHQ statutory footing for the first time, decades after their creation, and set out their functions and authorisation procedures for their activities. The same Act created the Intelligence and Security Committee (ISC) of Parliament to oversee all three agencies. It marked the end of official government refusal to confirm MI6's existence.

## 24 September 2002 — Iraq weapons dossier published

The government published a dossier on Iraq's weapons capabilities, drawing on assessments from the Joint Intelligence Committee, which included a widely publicised claim that Iraq could deploy chemical or biological weapons within 45 minutes of an order to do so. The dossier was used to support the case for the 2003 invasion of Iraq. No such weapons were found after the invasion, and the dossier's sourcing and drafting later became the subject of official inquiries.

## 18 July 2003 — David Kelly dies amid Iraq dossier row

Government weapons scientist David Kelly was found dead after being named as the likely source for a BBC report alleging the Iraq dossier had been embellished by Downing Street. The Hutton Inquiry into his death concluded he took his own life and largely cleared the government of wrongdoing, though its findings were criticised by some as too favourable to ministers. The episode intensified public scrutiny of how intelligence assessments had been used to justify the Iraq war.

## 14 July 2004 — Butler Review criticises Iraq intelligence

The Butler Review, chaired by former Cabinet Secretary Lord Butler, reported on the use of intelligence in the run-up to the Iraq war. It found the 45-minute claim should not have been included without clearer caveats and identified weaknesses in the intelligence assessment process, while stopping short of blaming individuals by name. The review led to reforms in how the Joint Intelligence Committee assessed and presented raw intelligence.

## 7 July 2005 — 7 July bombings expose prior MI5 contact with plotters

Four suicide bombers killed 52 people on London's transport network. Subsequent Intelligence and Security Committee reviews found that MI5 had previously come across two of the bombers during other investigations but had not judged them a priority for further inquiry, prompting criticism of resource allocation and information sharing within the Service. The findings led to changes in how MI5 triaged leads on domestic extremism.

## 1 November 2006 — Alexander Litvinenko poisoned in London

Former FSB officer and Kremlin critic Alexander Litvinenko was poisoned with radioactive polonium-210 in London and died three weeks later. A 2016 UK public inquiry led by Sir Robert Owen concluded the killing was probably approved by the Russian state and named two Russian suspects. The case raised questions about the British security agencies' ability to protect defectors and dissidents living in the UK.

## 10 February 2010 — Court of Appeal rules MI5 knew of Binyam Mohamed's torture

The Court of Appeal ordered the disclosure of a summary showing UK intelligence officers had known of the mistreatment of British resident Binyam Mohamed during his detention and interrogation abroad after 9/11. The ruling was part of a wider set of legal cases alleging British agencies were complicit in the rendition and torture of terrorism suspects held by other countries. The government maintained it did not condone torture but faced sustained litigation and settlements over the allegations.

## 6 July 2010 — Government announces detainee inquiry into rendition claims

Prime Minister David Cameron announced an inquiry, chaired by retired judge Sir Peter Gibson, into whether British intelligence agencies were implicated in the rendition and mistreatment of detainees after 9/11. The inquiry was suspended in 2012 amid ongoing police investigations and its work was later folded into review by the Intelligence and Security Committee, which published its own findings on the allegations in 2018.

## 25 April 2013 — Justice and Security Act strengthens ISC oversight

The Justice and Security Act 2013 reformed the Intelligence and Security Committee, turning it into a committee of Parliament rather than a body appointed by and reporting to the Prime Minister, and expanding its remit to cover operational matters. The Act also introduced closed material procedures allowing sensitive intelligence evidence to be heard in civil courts without full disclosure to the other side, a change that drew criticism from civil liberties groups.

## 5 June 2013 — Edward Snowden leaks begin

The Guardian publishes the first of a series of stories, sourced from documents leaked by former NSA contractor Edward Snowden, revealing that the NSA collects the phone records of millions of Americans in bulk under a secret court order. Snowden identifies himself as the source days later and is charged with espionage; he remains in exile in Russia.

## 21 June 2013 — Guardian reveals GCHQ's Tempora programme

Drawing on Snowden's leaked documents, the Guardian reported that GCHQ had been secretly tapping fibre-optic cables carrying transatlantic internet and phone traffic under a programme codenamed Tempora, storing vast amounts of communications data and sharing access with the NSA. The programme had reportedly been operating since around 2011 without public knowledge or specific parliamentary debate. It became the centrepiece of the British side of the Snowden surveillance disclosures.

## 6 February 2015 — Tribunal rules prior GCHQ-NSA data sharing unlawful

The Investigatory Powers Tribunal ruled that GCHQ's receipt of intercepted communications data from the NSA had been unlawful before December 2014, because the rules governing the arrangement had not been sufficiently public until disclosed in the course of the litigation. It was the first time the secretive tribunal had ruled against a UK intelligence agency. The ruling did not affect the legality of the underlying data collection itself, only the earlier lack of published safeguards.

## 29 November 2016 — Investigatory Powers Act becomes law

Parliament passed the Investigatory Powers Act 2016, which put GCHQ's bulk interception, bulk data acquisition, and equipment interference powers on an explicit statutory footing for the first time and created a system of judicial approval for the most intrusive warrants. Nicknamed the Snoopers' Charter by critics, the Act was the government's legislative response to the legal and political fallout from the Snowden revelations. Civil liberties groups continued to challenge aspects of the Act in the courts after it passed.