SIS (MI6, Secret Intelligence Service)

History

SIS says that it was founded in the early twentieth century as part of the Secret Service Bureau and developed during both world wars. Its list of chiefs begins with Sir Mansfield Cumming, the first “C”, in 1909; there have been eighteen chiefs to date.^2,3

According to SIS, Cumming is the origin of the name “CX” for its reports (Cumming’s Exclusives) and of the custom of the Chief signing in green ink.²

The Intelligence Services Act 1994 was the first public acknowledgement of the existence of MI6 and GCHQ. In July 1994 Queen Elizabeth II opened the new SIS headquarters at Vauxhall Cross.³

Functions and status

Under section 1 of the Act, SIS operates under the authority of the Secretary of State. It obtains and provides information relating to the actions or intentions of persons outside the British Islands and performs other tasks relating to them – solely in the interests of national security (with particular reference to defence and foreign policy), in the interests of the country’s economic well-being, or in support of the prevention or detection of serious crime.¹

It is headed by a Chief appointed by the Secretary of State, who is responsible for the efficiency of the Service and for ensuring that it takes no action to further the interests of any political party (section 2). The Chief is the only publicly named member of SIS and reports directly to the Foreign Secretary.^1,2

According to the SIS website (as of 4 November 2026), the Chief is Blaise Metreweli, a career intelligence officer who joined the Service in 1999 and was previously Director General for Technology and Innovation (“Q”).²

Oversight

SIS is overseen by the Intelligence and Security Committee of Parliament – the same committee that oversees MI5 and GCHQ.⁴