Security Service
Mi5 crest and logotype.svg
Thames House and Lambeth Bridge, looking across the river.jpg
Thames House, London
Agency overview
Formed1909 as the Secret Service Bureau
JurisdictionHer Majesty's Government
HeadquartersThames House, London, UK
MottoRegnum Defende ("Defence of the Realm")
Employees4,053 (31 March 2016)[1]
Annual budgetSingle Intelligence Account (£2.6 billion in 2014–2015 financial year)[2]
Minister responsible
Agency executive

The Security Service, also known as MI5 (Military Intelligence, Section 5),[3] is the United Kingdom's domestic counter-intelligence and security agency and is part of its intelligence machinery alongside the Secret Intelligence Service (MI6), Government Communications Headquarters (GCHQ) and Defence Intelligence (DI). MI5 is directed by the Joint Intelligence Committee (JIC), and the service is bound by the Security Service Act 1989. The service is directed to protect British parliamentary democracy and economic interests, and counter terrorism and espionage within the UK.

Within the civil service community the service is colloquially known as Box 500 (after its official wartime address of PO Box 500; its current address is PO Box 3255, London SW1P 1AE).[4]

The service has had a national headquarters at Thames House on Millbank in London since 1995, drawing together personnel from a number of locations into a single HQ facility: Thames House also houses the Joint Terrorism Analysis Centre, a subordinate organisation to the Security Service; prior to March 2013, Thames House additionally housed the Northern Ireland Office (NIO). The service has offices across the United Kingdom including an HQ in Northern Ireland.[5]

Details of the northern operations centre in Greater Manchester were revealed by the firm who built it.[6]


The Security Service comes under the authority of the Home Secretary within the Cabinet.[7] The service is headed by a Director General at the grade of a Permanent Secretary of the British Civil Service who is directly supported by an internal security organisation, secretariat, legal advisory branch and information services branch. The Deputy Director General is responsible for the operational activity of the service, being responsible for four branches; international counter-terrorism, National Security Advice Centre (counter proliferation and counter espionage), Irish and domestic counter-terrorism and technical and surveillance operations.[8]

The service is directed by the Joint Intelligence Committee[9] for intelligence operational priorities. It liaises with SIS, GCHQ, DIS, and a number of other bodies within the British government and industrial base. It is overseen by the Intelligence and Security Committee of Members of Parliament, who are directly appointed by the Prime Minister, by the Interception of Communications Commissioner, and by the Intelligence Services Commissioner. Judicial oversight of the service's conduct is exercised by the Investigatory Powers Tribunal.[10]

Operations of the service are required to be proportionate and compliant with British legislation including the Regulation of Investigatory Powers Act 2000, the Data Protection Act 1998, and various other items of legislation. Information held by the service is exempt from disclosure under section 23 of the Freedom of Information Act 2000.[11]

All employees of the service are bound by the Official Secrets Act.[12] In certain circumstances, employees can be authorised to carry out activity which would otherwise be criminal within the UK.[13]

The current Director General is Andrew Parker, who succeeded Jonathan Evans on 22 April 2013.[14]

The service marked its centenary in 2009 by publishing an official history titled The Defence of the Realm: The Authorized History of MI5 and written by Christopher Andrew, Professor of Modern and Contemporary History at Cambridge University.[15]

Other Languages
azərbaycanca: MI5
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dansk: MI5
eesti: MI5
Ελληνικά: Security Service
español: MI5
Esperanto: MI5
euskara: MI5
فارسی: ام‌آی۵
français: Security Service
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한국어: MI5
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Bahasa Indonesia: MI5
italiano: MI5
עברית: MI5
Jawa: MI5
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lietuvių: MI5
Nederlands: Security Service
norsk: MI5
norsk nynorsk: MI5
português: MI5
русский: MI5
Scots: MI5
shqip: MI5
Simple English: MI5
slovenščina: MI5
српски / srpski: MI5
srpskohrvatski / српскохрватски: MI5
Türkçe: MI5
українська: MI5
Tiếng Việt: MI5
中文: 軍情五處