[7] Unlike its main sister agencies, Security Service (MI5) and Government Communications Headquarters (GCHQ), SIS works exclusively in foreign intelligence gathering; the ISA allows it to carry out operations only against persons outside the British Islands.

It provides the British government with vital intelligence regarding foreign events and informs concerning global covert capabilities to uphold national interests, security and protect the country's economic well-being.

[13] SIS has three primary tasks:[12] The impact and success in these situations helps to prevent hostile influence, keep the UK's defences on alert to reduce serious and organised crime, and to detect violations of international law.

[22] Due to security concerns, the Government does not publish these financial statements which are audited by the Comptroller and Auditor General and then shown to the chair of the Public Accounts Committee in accordance with the Intelligence Services Act 1994.

[4] 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.

[34] 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.

Sinclair created the following sections: In 1924, MI6 intervened in the general election of that year by leaking the so-called Zinoviev letter to the Daily Mail, which published it on its front page on 25 October 1924.

[41] The Zinoviev letter played a key role in the defeat of the minority Labour government of Ramsay MacDonald and the victory of the Conservatives under Stanley Baldwin in the general election of 29 October 1924.

[51] The "limited liability" rearmament policy pursued by the Chamberlain government had intentionally starved the British Army of funds to rule out the "continental commitment" (i.e. Britain sending a large expeditionary force) from ever being made again, with the majority of military spending being devoted to the RAF and the Royal Navy.

[53] One of MI6’s most successful operations before the war started in April 1939 when an Australian businessman living in London, Sidney Cotton, who was already engaged in aerial photographic espionage for the Deuxième Bureau was recruited to fly missions over Germany.

Notably, Polish secret agent Jan Karski played a crucial role in delivering the first Allied intelligence on the Holocaust, providing the British with harrowing information about Nazi atrocities.

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.

[76] Menzies who fiercely defended the prerogatives of MI6 was able to block this proposal despite the way it was universally accepted by officers serving in the China-Burma-India theater that SIS was unsuitable to operating in that part of the world.

As part of British government efforts to stem this migration, Operation Embarrass saw the SIS bomb five ships in Italy in 1947–48 to prevent them being used by the refugees, and set up a fake Palestinian group to take responsibility for the attacks.

[83] SIS operations against the USSR were extensively compromised by the presence of an agent working for the Soviet Union, Harold Adrian Russell "Kim" Philby, in the post-war Counter-Espionage Section, R5.

SIS suffered further embarrassment when it was revealed 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.

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.

[102] Two days after the interview, he was sent instructions, copied to all MI5 and MI6 officers in Afghanistan, about how to solve concerns over mistreatment, referring to signs of abuse: "Given that they are not within our custody or control, the law does not require you to intervene to protect this."

MI6 personnel in the country never exceeded 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 networks 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 of Pakistan based terrorist group.

[105] Shortly before the Second Battle of Fallujah, MI6 personnel visited JSOCs TSF (Temporary Screening Facility) at Balad Air Base to question a suspected insurgent.

[113] 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.

This development was a consequence of their public identification in various media reports, a situation that arose due to the actions of disgruntled local intelligence services, especially in Croatia and Serbia.

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'.

[119] 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.

[120] Five years before the Libyan Civil War, a UK Special Forces unit was formed called E Squadron which was composed of selected members of the 22nd SAS Regiment, the SBS and the SRR.

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, so the outcome is unknown.

A British academic, Matthew Hedges questioned the UK's training programme for allowing officials of the UAE, where he was detained on false charges and faced psychological torture.

[136] A Year with MI6 was a public art exhibition, showing a collection of paintings and drawings by artist James Hart Dyke to mark the centenary of the Secret Intelligence Service.

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.

Leo Marks explains in his World War II memoir Between Silk and Cyanide that the name arose because a section of the Special Operations Executive (SOE) was housed in a building at 1 Dorset Square, London, which had formerly belonged to the directors of Bertram Mills circus.