These pages describe two elements in the security apparatus of the United Kingdom. Internal security is the province of the Security Service (MI5), while espionage against overseas targets is undertaken by MI6, the Secret Intelligence Service.

MI5: Security Service

Thames House on Millbank, the London headquarters of the Security Service

MI5's first responsibility since its founding in 1909 has been to counter penetration of UK organisations by foreign intelligence services. It has gained a wider remit covering national security issues, much of its resources today being focused on terrorism, both Muslim and also Northern Irish.

The Security Service has since 1995 occupied Thames House in central London, not far from the Palace of Westminster. Today 3,600 people work for MI5, increasing to 4,100 in 2011 with the expansion of the war on Muslim terrorism. The current Director General is Jonathan Evans who answers to the Home Secretary, in theory at least. There have been reports that MI5 officers have been involved in the torture of suspects.

Follow this link for further information on MI5.

MI6: Secret Intelligence Service

Vauxhall Cross MI6 HQ

MI6, the Secret Intelligence Service, came into being in 1909 to undertake espionage activities overseas. Today its role is defined by the Intelligence Services Act 1994 as "to obtain and provide information relating to the actions or intentions of persons outside the British Islands, and perform other tasks relating to these in relation to the interests of national security".

The SIS is located at Vauxhall Cross in London, and its chief is John Scarlett. The focus of MI6's activities has been the Russian threat, but this has now been cut back significantly. Unlike MI5, SIS still retains a role in support of the prevention or detection of serious crime.

Follow this link for further information on MI6.

Where to find them


MI5 and MI6 offices in central London

MI5's headquarters is Thames House on Millbank, a modernised listed building located on the south-west end of Lambeth Bridge. In the main entrance you will observe a closed-circuit TV camera directed aggressively at passers-by.

MI6's head office is a rather unusual-looking edifice on Vauxhall Cross, immediately apparent on exiting the tube station. The new 200M million building was designed by architect Terry Farrell.

How to contact them

MI5 and MI6 are usually contacted by post. MI5 also publishes a "hotline" telephone number. Neither MI5 nor MI6 give out email addresses.

MI5's postal address is;

MI5 / Security Service
PO Box 3255
London SW1P 1AE

The telephone hotline number for MI5 was given on the front page of The Times of March 11, 1998, in article which says the number is intended for "terrorists, spies and serious criminals" and not "ordinary members of the public". It is;


MI6's postal address, as given by the British Foreign Office, is;

PO Box 1300
London SE1 1BD

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