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 on foreign nationals in support of its Five Eyes partners. SIS is one of the British intelligence agencies and the Chief of the Secret Intelligence Service ("C") is directly accountable to the Foreign Secretary.

Government Communications Headquarters (GCHQ) is an intelligence and security organisation responsible for providing signals intelligence (SIGINT) and information assurance (IA) to the government and armed forces of the United Kingdom. Primarily based at "The Doughnut" in the suburbs of Cheltenham, GCHQ is the responsibility of the country's Secretary of State for Foreign and Commonwealth Affairs, but it is not a part of the Foreign Office and its Director ranks as a Permanent Secretary.