Where we work

River with building in background

Our locations

More than 5,000 people work for MI5. While most of our staff are based in one of our offices in London, we have teams located across the UK. We also have staff based around the world. 

Thames House 

Thames House, in central London, is our headquarters. It was opened by the Prime Minister in 1994, a few years after our existence was first officially confirmed in legislation.

CTOC logo In 2021, we opened the Counter Terrorism Operations Centre, a world-leading facility where the UK’s intelligence community works alongside colleagues in the police and with other operational partners. This allows for minute-by-minute collaboration on counter-terrorism operations.


Belfast at nightWe have several teams based on Northern Ireland, working to respond to a range of different national security threats, including but not limited to the threat from Northern Ireland-related terrorism. Investigations are directed from our office in Palace Barracks, just outside Belfast, where we work in close partnership with the Police Service of Northern Ireland alongside other agencies.


We have a network of regional offices around the country and there are also MI5 officers based around the world to enable collaboration with our international partners.