# MI6 The Secret Intelligence Service (SIS), commonly known as MI6, is the United Kingdom's foreign intelligence agency — responsible for gathering human intelligence (HUMINT) abroad and conducting covert operations in support of British national security and foreign policy. It is the British equivalent of the [[CIA]] and one of the oldest continuously operating intelligence services in the world. The "MI6" designation derives from the agency's World War I origin as Military Intelligence, Section 6 — the branch responsible for overseas intelligence. The agency's chief is traditionally known only as "C," a convention dating to the first director, Captain Sir Mansfield Cumming, who signed documents with a single green-ink "C." The British government did not officially acknowledge MI6's existence until 1994, when the Intelligence Services Act placed it on a statutory footing. ## Mission and structure MI6 conducts human intelligence collection worldwide, running agents (recruited sources) inside foreign governments, militaries, intelligence services, and terrorist organizations. It also conducts covert action — sabotage, influence operations, and support to resistance movements — when authorized by the Foreign Secretary. Post-9/11, counterterrorism became a dominant mission alongside traditional state-on-state espionage. The agency operates under the authority of the Foreign, Commonwealth and Development Office and is overseen by the Intelligence and Security Committee of Parliament. Its headquarters since 1994 is the distinctive Vauxhall Cross building on the south bank of the Thames — perhaps the world's most recognizable intelligence facility thanks to the James Bond franchise, which has shaped public perception of MI6 more than any real operation. ## Historical significance MI6's operational history spans over a century: running double agents against Nazi Germany, managing the Cambridge Five mole hunt (Kim Philby, Donald Maclean, Guy Burgess, Anthony Blunt, John Cairncross — Soviet agents who penetrated the highest levels of British intelligence), orchestrating the 1953 Iranian coup alongside the [[CIA]] (Operation Boot/Ajax that installed the Shah and ultimately produced [[SAVAK]]), and conducting Cold War operations across Eastern Europe. The Philby affair — in which the head of MI6's anti-Soviet section was himself a Soviet agent — remains the most damaging intelligence penetration in Western history and shaped the institutional culture of suspicion and compartmentation that defines modern intelligence services. ## KB relevance MI6 matters to the vault primarily through the [[Five Eyes Alliance]] — Britain is the US's closest intelligence partner, with a level of integration that effectively makes MI6 and the [[CIA]] extensions of each other for many operational purposes. The Christopher [[Steele Dossier]] on Trump-Russia connections was produced by a former MI6 officer, making the agency a node in the [[Crossfire Hurricane]] investigation and a target of right-wing conspiracy theories about foreign interference in American politics. The irony: the actual foreign interference came from the [[GRU]] and [[FSB]], not MI6. ## See Also - [[MI5]] — UK domestic intelligence - [[GCHQ]] — UK signals intelligence - [[CIA]] — US equivalent - [[Five Eyes Alliance]] — the intelligence-sharing framework - [[SAVAK]] — the Iranian secret police MI6 helped create - [[Global Intelligence Hub]] — full agency index