A Few Important Dates in History
The Security Service (MI5), a domestic intelligence service, and Secret Intelligence Service (MI6), a foreign intelligence service, are formed.
Government Code and Cypher School (GC&CS), a signals intelligence organization, was formed. This organization was later renamed to Government Communications Headquarters (GCHQ).
MI5's importance rapidly increases to counter Soviet espionage.
Joint Intelligence Committee (JIC) forms. JIC is primarily responsible for intelligence assessment.
Despite being initially unprepared, MI5's mission played a key role in countering espionage tactics during World War II. MI6's human intelligence (HUMINT) efforts are complemented by MI5.
Operation Gold, a joint operation by the Central Intelligence Agency and MI6 begins. The operation was created to tap into a Soviet Army communications line (via a tunnel system) to steal critical intelligence.
Operation Gold is compromised.
Defence Intelligence (DI) organization forms. DI is responsible for gathering and analyzing military intelligence.
New legislation passes to enable MI5 to extend their security services (i.e., signals intelligence/surveillance) to other intelligence agencies.
After the terrorist attacks in September 2001, MI5 begins collecting bulk telephone records (bulk personal datasets, or BPDs) as per the powers granted to them under the Security Service Act of 1989 and Intelligence Services Act of 1994.
Andrew Parker takes the position as Director General of the Security Service (MI5).
Alex Younger begins his role as Chief of the Secret Intelligence Service (MI6).
Signals intelligence (SIGINT), somewhat similar to the National Security Agency (NSA). "Using our expertise and experience GCHQ is part of the team which protects the UK, along with law enforcement and the other intelligence agencies. Working with HMG and industry, we defend Government systems from cyber threat, provide support to the Armed Forces and strive to keep the public safe, in real life and online."
Security Service (MI5) Mission
Domestic intelligence. "The role of MI5, as defined in the Security Service Act 1989, is the protection of national security and in particular its protection against threats such as terrorism, espionage and sabotage, the activities of agents of foreign powers, and from actions intended to overthrow or undermine parliamentary democracy by political, industrial or violent means."
Secret Intelligence Service (MI6) Mission
Foreign intelligence. "We work secretly overseas, developing foreign contacts and gathering intelligence that helps to make the UK safer and more prosperous. We help the UK identify and exploit opportunities as well as navigate risks to our national security, military effectiveness and economy. We work across the globe to counter terrorism, resolve international conflict and prevent the spread of nuclear and other non-conventional weapons."
Jeremy Fleming, head of the British Government Communications Headquarters.
Andrew Parker, Director-General of the British Security Service.
Alex Younger, Chief of the Secret Intelligence Service.