Thames House, headquarters of MI5/Secret Service
Some other major structural alterations were made and because of its use by MI5 the building was reinforced to carry heavy plant and computer equipment, strengthened against attack and fitted with specialist equipment of similar nature to the HQ of SIS at Vauxhall Cross. Thames House is not just an office block for the desk officers. It contains computer rooms, technical areas and laboratories, workshops, training areas and probably a lot more that is secret. The air conditioning has been produced to specialist requirements with extra resilience, and there is secondary glazing inside the windows for bomb blast protection. At the back is a service entrance leading to a basement which houses an underground car park of secure garaging. Also, as can be seen in the photos, Thames House is frequently guarded by armed police.
Thames House was officially opened in 1994 and the Service carries responsibilities across a number of different organisations including 50 Special Branches, Customs and Defence Intelligence. According to the book Defending the Realm (which may be out of date) there are many departments dealing with threats from all over the world as well as inside the UK. The departments are designated with a letter according to which area of expertise they cover, roughly as follows:
A: Telephone tapping, covert entry, etc
B: Protective security for MI5 and vetting of MI5 staff
D: Non-terrorist investigations.
F: Political subversives
G: Counter-terrorism, international terrorism
H: Covert financial inquiries eg financial institutions.
T: Countering IRA and Loyalist groups, arms trafficking
R: Main registry, files, GCHQ files.
MI5 also works closely with Special Branch, of the police. Special Branch are said to be street operatives for the Security Service providing covert observation. SB can tap into regional networks of information, supply intelligence from local informants, enforce the Prevention of Terrorism Act and the Official Secrets Act. The relationship is quite interesting, as shown in this quote:
‘While SBs investigate individuals and organisations that could present a threat to public order, the Security Service would not investigate these bodies unless they posed a threat to national security. This means that not all intelligence collected by SBs is or can be shared with the Security Service’.
(Committee report on Intelligence Services 2003)
For more information about Thames House, MI5 and the work they do see their official website at