About Us

The people of MI5

MI5 exists to protect the UK from threats to our national security, primarily terrorism and threats posed by states.

More than 5,000 people work at MI5, bringing together people with lots of different backgrounds, and lots of different skills. Everyone at MI5 has the same mission: to keep the country safe.

We have roles that you will not find anywhere else, like our investigators and surveillance officers. We also have roles that you’d expect to see at any large organisation, like data analysts and, of course, the security officers who work to keep our buildings safe. You can find out more about the jobs we have and what it’s like to work at MI5 on our careers pages.


Ken McCallum giving speech

Director General

The head of MI5 is the Director General. We know them as 'the DG' and they are our only member of staff whose identity is made public. The identity of everyone else who works for MI5 is kept secret so that we can carry out our operational work covertly and effectively. The current Director General is Ken McCallum.


We were established in 1909 as the Security Service Bureau. Our functions were first included in legislation in the 1989 Security Service Act which said: “there shall continue to be a Security Service”.

 Our tools and powers are set out in legislation and are subject to robust oversight arrangements.

Office building in city

Where we work

MI5’s headquarters are at Thames House in central London. We also have several regional offices around the UK, including one in Northern Ireland.

Logos of SIS and GCHQ


We work with lots of other organisations to help keep the country safe. This includes the UK’s other intelligence agencies, SIS and GCHQ as well as the police and government departments. We also work with the private sector and academic institutions.