To report an imminent threat call 999 or ring the Anti-Terrorist Hotline on 0800 789 321
Current UK threat level: SEVERE Read more about threat levels >>

WHAT'S IN A NAME?

The Security Service has had a variety of names, most famously MI5, since it was established in 1909. This has often led to confusion about what the Service has been called at various points in its history.

October 1909

The Security Service is founded as the Home Section of the Secret Service Bureau, under Captain Vernon Kell. (See "The establishment of the Secret Service Bureau"). It is placed under the nominal supervision of the Directorate of Military Operations of the War Office, the predecessor of today's Ministry of Defence. The branch of the DMO responsible for the Secret Service Bureau is called MO5.

April 1914

The Secret Service Bureau is absorbed into the War Office for the duration of the war. It becomes part of section 5 of the Directorate of Military Operations and is given the name MO5(g).

September 1916

MO5(g) is moved across to the newly established Directorate of Military Intelligence within the War Office. It becomes section 5 of the Directorate of Military Intelligence - hence MI5.

1929

MI5 is renamed as the Defence Security Service.

1931

The Defence Security Service becomes the Security Service, the name by which it is still known today. However, "MI5" is still widely used as a short alternative to our official name.

Fact or Fiction?
MI5 and SIS do basically the same thing, but in different places.

True False

Latest News

view ALL News

MI5 wins LGBT British Employer of the Year

MI5 has been named Employer of the Year at the 2018 British LGBT Awards.

Read Full Article ›

Director General Andrew Parker Speech to BfV Symposium

Director General Andrew Parker gave a speech to the BfV Symposium in Berlin on 14 May 2018.

Read Full Article ›