Inside MI5 - what they do, how they work and misconceptions

Inside MI5 - the real Spooks

Many of us have watched or read spy thrillers and movies and wonder what its like inside the secretive buildings of Thames House or Milbank. The security services exist and do their work to keep you and I, the public safe. Therefore we are not seeking to 'expose' their work, just rather discuss what they do - and help clear up the misconceptions that the TV or movies give.

Since the July 7th attacks in 2005, MI5's main focus has been on Counter terrorism. Counter terrorism work for MI5 is involved in 3 main key areas:

Islamist terrorism - "the most significant terrorist threat to the UK by volume" [1]
Northern Ireland-related terrorism
Extreme right wing terrorism

Left wing terrorism "makes up a significantly smaller portion of our casework" [1]

Whereas before MI5 was just based (exclusively) in Thames House London, they have now setup 'a network of regional offices across the UK, including an office in Northern Ireland'. The MI5 Northern Ireland office has received much press and its location is widely known, however the others are not. We know they exist in each of the regions but their towns or precise locations are unknown.

We do however know of the former location of the Birmingham MI5 office as it has since been converted into flats! It gives a good idea of the type of building they operated out (see below) of [3].

However as of December 2024, according to the Times, "MI5 has been forced to “pare back” its focus on counterterrorism to deal with the growing threat posed by Russia and other hostile states". Clearly the "hybrid" war as it could become known is increasing and MI5 is having to change course. [4]

To change the date on the Google Streetview features, click the "View in Google Maps" option and note the dates on this section:

MI5 Headquarters

Former MI5 Office Birmingham [2008]

What does MI5 do?

Based on [2]

MI5 and Police have stopped 43 "late-stage" terrorist attacks since 2017
75% of the counter terrorism work relates to Islamic Extremism
Since Jan 2022 - potentially 20 lethal "Iran backed" plots
Russia uses organised crime to achieve its goals
1 in 8 of their investigations involve people under the age of 18

The former MI5 based BBC drama Spooks, portrays a few gun running saving the day. MI5 simply do not have that role don't run around with guns and also don't have power to arrest. In fact they now work much closer with the police so that although what happens in Spooks may happen over the course of an operation - it is not limited to just one organisation.

MI5 operations take a long time to prepare, there are lots of official forms to fill out explaining why someone or organisation should be tracked or bugged. Each request has to go to the Home Secretary to permit as it is technically a breach of human rights.

MI5 takes the lead in gathering and analysing intelligence. MI5 is concerned with analysing leads, whereas the police are concerned with suspects. MI5 investigate a huge number of individuals and decide whether they should be arrested and pose a threat to the UK. If they do, the case is referred to the police who take the lead in developing that intelligence. Effectively there will be similarities in what they do, however the latter is focused on specific individuals.

How MI5 work

Intelligence could come from a number of difference sources (considered by the author):

MI6/GCHQ - individuals could be tracked abroad generating suspicious activity
Anti terrorism hotline - members of the public can report activity
Existing surveillance - maybe MI5 are watching a group and a new individual comes on to the scene - are they a threat or simply an innocent member of the public?
Internet chatter - forums and websites could be monitored that generate interest in an individual or group
Prisons

These are just a few and each example could create many leads each of which needs prioritising and analysing. If you imagine intelligence as a funnel - MI5 is at the top and the police look after the ones at the bottom.

According to MI5's official website the 4 main ways MI5 collect intelligence are:

Human intelligence sources (agents) - people (not employed by MI5) who report from inside target groups and organisations
Directed surveillance - mobile operations (car / on foot surveillance) - they often work closely with the police on this
Intercepting communications
Intrusive surveillance - bugging a home or car

Once this intelligence has been gathered it must be analysed. All of which takes along time - unlike the hour episodes of Spooks!

We know that the vehicles MI5 use are serviced at a Garage. See our secret bases page for the known location of the previous MI5 garage.

Mobile surveillance is often supported by the police but according the Mirror can even include 'the army and its special reconnaissance regiment'. This unit has a history in Northern Ireland where it supported the SAS in transport and surveillance. We know that when Jean Charles Dimenez was being followed by the MET they were accompanied by members of the military, and its rumoured these were members of the SRR.

Having read the book "The Terrorist Hunters" - it provides an insight into the world of mobile surveillance which unlike the idealised picture we might have gives a picture of long hours sat in solitude in cars, not going anywhere for loo breaks and getting muscle pain from sitting for so long. Hardly the James bond picture we can have of the work of spies!

Working with others

The point at which a lead becomes a suspect may vary with each case. A group called an Executive Liaison Group 'enable MI5 to safely share secret, sensitive, and often raw intelligence with the police, on which decisions can be made about how best to gather evidence and prosecute suspects in the courts. Each organization works in partnership throughout the investigation, but MI5 retain the lead for collecting, assessing and exploiting intelligence. The police take lead responsibility for gathering evidence, obtaining arrests and preventing risks to the public.'

It is also this group which 'make a formal decision about when responsibility for the tactical direction of the overall investigation should transfer from MI5 to the police, and also decide when to take executive action (e.g. arrest suspects).'

Thus there is much liaison between the police and MI5 and this is widely known and even mentioned in job descriptions for MI5 jobs. Nothing super secret here then! The MI5 website mentions (as part of its recruitment section) 'Working in one of our regional offices could involve managing the liaison with a regional police Special Branch Counter Terrorist Unit. In order to progress investigations you could attend casework meetings with police to help to prioritise our investigative work, as well as deliver feedback to the analysts who supply us with intelligence.'

Garages and cars

MI5 is a very secretive organisation, but over the last few years its shape and structure have changed dramatically. The rise in terrorism has forced MI5 to work much closer with the police and as such, the organisation has expanded outside of London.

MI5 have always had a garage where it works on its vehicles for those members of its staff (known as the Watchers) who according to the MI5 website "Mobile Surveillance Officers are a key investigative resource. They follow targets of national security investigations. It is all about observing people and places, either on foot or by vehicle." According to Alan Turnballs website the garage in the 70's was located in Barnard Road, Clapham.

Following on from this, MI5's garage moved to Streatham high street. Thanks to Bing Maps we can see what the site looked like (unfortunately after it had been cleared of cars).

Streatham garage 1 [Src: Bing Maps].

Thanks to Google Streetview, we can see it is now a Storage facility and has since been relocated to somewhere in "West London" according to their adverts.

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