Secret Intelligence Service

London's SIS Building, a postmodern fortress on the Thames, has been the operational heart of the Secret Intelligence Service since 1994. Known universally as MI6, the agency gathers human intelligence overseas to protect UK national security. Its chief, always called "C," reports directly to the foreign secretary. Unlike MI5, which handles domestic security, or GCHQ, which focuses on signals intercepts, MI6 operates exclusively outside British borders.

MI6 began in 1909 as the Foreign Section of the Secret Service Bureau, split off from the domestic section in 1910. Mansfield Smith-Cumming, the first chief, signed documents in green ink with a single "C", a tradition every successor has kept. The label MI6 emerged during World War II from "Military Intelligence, Section 6" and stuck in popular culture. The UK government officially denied the agency's existence until 1994, when the Intelligence Services Act placed it on a statutory footing and brought it under legal oversight for the first time. Today, the Investigatory Powers Tribunal and the Intelligence and Security Committee of Parliament monitor its work.

MI6's priorities include counter-terrorism, counter-proliferation of nuclear and chemical weapons, cyber intelligence, and disrupting criminal networks. It works closely with Five Eyes partners, the US, Canada, Australia, and New Zealand. But the agency has faced serious controversies: flawed Iraq WMD intelligence that led to the 2004 Butler Review, and allegations of complicity in torture and extraordinary rendition after 9/11, including the case of Binyam Mohamed. A 2018 parliamentary report found MI6 officers were involved in mistreatment of detainees.[edit]