The Secret Intelligence Service (SIS), commonly known as MI6, is the foreign intelligence service of the United Kingdom, tasked mainly with the covert overseas collection and analysis of human intelligence (HUMINT) in support of the UK's national security. SIS is a member of the country's intelligence community and its Chief is directly accountable to the Foreign Secretary.

Formed in 1909 as the foreign section of the Secret Service Bureau, the section experienced dramatic growth during World War I and officially adopted its current name around 1920. The name "MI6" (meaning Military Intelligence, Section 6) originated as a flag of convenience during World War II, when SIS was known by many names. It is still commonly used today. The existence of SIS was not officially acknowledged until 1994. That year the Intelligence Services Act 1994 (ISA) was introduced to Parliament, to place the organization on a statutory footing for the first time. It provides the legal basis for its operations. Today, SIS is subject to public oversight by the Investigatory Powers Tribunal and the Parliamentary Intelligence and Security Committee.

The stated priority roles of SIS are counter-terrorism, counter-proliferation, providing intelligence in support of cyber security, and supporting stability overseas to disrupt terrorism and other criminal activities.[8] Unlike its main sister agencies, the Security Service (MI5, "Box 500") 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. Some of SIS's actions since the 2000s have attracted significant controversy, such as its alleged complicity in acts of torture and extraordinary rendition.

Since 1994, SIS has been headquartered in the SIS Building in London, on the South Bank of the River Thames. [1]

Sources

[1] https://en.wikipedia.org/wiki/Secret_Intelligence_Service