Thames House, HQ of MI5

Thames House, headquarters of MI5/Secret Service


Thames House on Millbank, seen at sunset from the South Bank of the river. The bridge in the foreground is Lambeth Bridge. Thames House broods on the northern bank of the river, a Grade 2 listed building designed by Sir Frank Baines. I rather like it. It’s quirky. It has a distinctive yellow roof (compared to cheese by an architectural historian) which I like to think of as a representation in stone of a cottage thatched roof. At the middle level every third window is decorated by half-columns and a metal-and-stone balcony. It looks as though the windows should open onto the balconies to let a group of Royals appear and give a wave to the masses below, like a mini-Buckingham Palace event.



A bizarre addition of columns on the upper floors give the impression there has been some sort of compromise, a feeling of really wanting larger columns at the bottom but not being able to afford them. Considering the buildings were built in the Depression years of 1929-30 it could well be the case that the architectural dream was restricted by lack of funds, or I could be wrong. Nevertheless, it conveys a sense of regal importance and according to MI5’s website ‘owes much to the Imperial Neoclassical style of Sir Edwin Lutyens, the designer of the Cenotaph on Whitehall’. It also has the added flair of a façade of Portland stone, a material which immediately bestows the description of ‘elegant’ on most buildings lucky enough to use it (you have to see it close up).



Entrance to Thames House – visitors do not go in through the main entrance but through one of the side doors. The façade is decorated with sculptures by Charles Sargeant Jagger and it displays a number of inscribed coats of arms with Latin mottos that reflect the building’s location and history. Thames House was constructed as two blocks connected by an archway. After it was bought by the Government for the Security Service in the 1980s and refurbished in the 1990s a new link block was built behind the archway, leaving the original feature untouched. As MI5’s headquarters the whole unified building was officially opened in 1994. The current Director General of MI5 is Jonathan Evans.



The entrance to Thames House with the link building seen clearly behind the archway. The distinctive archway has sculptural designs spanning the top. It’s another oddity but adds colour and interest to the overall uniformity of the lower walls.


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

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