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FAQs about MI5


If more than 50 years have passed, we may be able to say whether a relative used to work for us. Visit our contact page to find out more.

No. Sir Roger Hollis, the Director General of MI5 from 1956-1965 was investigated after allegations were made that either he or his deputy, Graham Mitchell, fitted the profile of a long-term Soviet agent. The allegations were made following the exposure of the so-called “Cambridge spy ring” and the subsequent hunt for other Soviet moles. 

The investigation lasted from 1964 to 1971 but came to no firm conclusions. The affair was reviewed in 1975 by Lord Trend, a former Cabinet Secretary, who found that there was no evidence to show that either Hollis or Mitchell had been Soviet agents.

An internal review carried out within MI5 in 1988 was strongly critical of the original investigation, concluding that the case against Hollis and Mitchell was "so insubstantial that it should not have been pursued". 

In the 1980s, KGB defector Oleg Gordievsky confirmed that Hollis had never been a Soviet agent. He has described how the Soviets themselves were baffled by the allegations against Hollis and attributed them to "some mysterious, internal British intrigue".

The neither confirm nor deny principle, also known as the NCND principle, is used to protect sensitive information and to prevent the damage to national security that would otherwise result from its disclosure. 

Information about who or what we are investigating, and the tools and techniques we use to carry out our investigations would be useful to the UK’s adversaries so we would not confirm details about our operations. 

It would mean those plotting attacks or conducting espionage could change their behaviour to avoid being detected. Keeping how we carry out our investigations secret helps us maintain an edge over the UK’s adversaries and helps to keep the country safe. 

Information about who works, or has worked, for MI5, or the identities of current and former covert human intelligence sources, also known as agents, would also be useful to those looking to do the country harm. It could also put the officers and agents concerned and their loved ones at personal risk, possibly endangering their lives. 

The NCND principle also means not denying both accurate and false claims about our operational activities. This is because if we did so once, then the absence of a denial in relation to other claims would be understood as confirmation that they were true. 

Therefore, MI5 will routinely apply the NCND principle when asked about its operations. The NCND principle has been consistently upheld by courts and tribunals. 

However, not everything we do is a secret. We make information about our work public where it stands to safeguard, rather than damage, national security. This includes information about what it’s like to work for us on this website and on our Instagram page so that potential recruits might consider working for us. From time to time, our Director General will share information about the threats the country faces, and what the public, businesses and other organisations can do to help keep the country safe. We will also disclose information to provide evidence in criminal prosecutions where doing so helps to protect, and does not damage, national security.

MI5 and MI6 are both intelligence agencies and often work closely together, but we have different missions. 

MI5 protects the UK's citizens and interests against national security threats (both at home and overseas) while SIS gathers intelligence overseas to support the government's security, defence, foreign and economic policies.

Our name dates back to the First World War. For part of the war, MI5 was the fifth branch of the Directorate of Military Intelligence of the War Office (the predecessor of today's Ministry of Defence). 

A number of other "MI" branches existed within this directorate. They were later discontinued or absorbed into other organisations, with the exception of our colleagues in SIS (MI6). 

We’re no longer part of the UK military establishment, although we do still contribute - along with the military - to the overall national security of the UK. We still use the name "MI5" as shorthand for our official name, the Security Service. 

See the history section of this website for more information.

MI5 was founded as the Home Section of the Secret Service Bureau. It was part of the War Office (the predecessor of today’s Ministry of Defence) in the First World War, between 1916 and 1918. During this time it was renamed MI5, referring to its status as the fifth branch of the Directorate of Military Intelligence. During the Second World War, MI5 was independent of the War Office, though it worked closely with it. 

There were several MI (Military Intelligence) sections within the War Office's Directorate of Military Intelligence during both the First and Second World Wars. There were eventually ten MI sections during the First World War and seventeen by the end of the Second World War. The number of MI sections and their precise functions varied considerably as the demands of the war effort changed. 

All of these sections, with the exception of our colleagues in SIS (MI6), were later discontinued or absorbed into other organisations.

In October 1909, Captain Vernon Kell of the South Staffordshire Regiment and Captain Mansfield Cumming of the Royal Navy jointly established the Secret Service Bureau following a recommendation by the Sub-committee of the Committee of Imperial Defence, which had been considering the danger from German espionage. 

To meet an additional requirement from the Admiralty for information about Germany's new navy, Kell and Cumming decided to divide up their work. Thereafter, Kell, or "K", was responsible for counter-espionage within the British Isles while Cumming, or "C", had responsibility for gathering intelligence overseas. The two divisions became MI5 and MI6 respectively. 

While the head of MI6 (SIS) is still referred to as "C" today, the Director General of MI5 has not been known as "K" since the 1940s. 

See The establishment of the Secret Service Bureau for the full story of how MI5 was founded.

The MI5 crest

The MI5 crest

The MI5 crest was designed by the late Rodney Dennys, the Somerset Herald of Arms. It was adopted in 1981 with the approval of the Garter Principal King of Arms. 

At the centre of the crest is a golden winged sea-lion on a blue background. This is not to be confused with the real sea lion (a type of seal) but is a mythological beast, half-lion and half-fish. It represents our historical association with the UK’s armed forces. The lion's head stands for the British Army, the fish's body for the Royal Navy, and the wings for the Royal Air Force. Gold traditionally represents virtue. The colour blue in the background signifies our overseas ties. 

Surrounding this central emblem are three further symbols: a green cinquefoil (a leaf with five petals), a portcullis and a red rose. 

  • The cinquefoil's five petals allude to the "5" in MI5. The colour green has been associated with intelligence since the First World War. 
  • The portcullis, traditionally a symbol of Parliament, relates to MI5's key task of upholding parliamentary democracy. The crown at the top of the uppermost portcullis refers to the Crown as an institution. 
  • The rose has historical associations with state intelligence work. Sir Francis Walsingham, Queen Elizabeth I's spymaster in the 16th century, used a rose as the seal on his signet ring. He is widely regarded as the first intelligence chief in British history. The rose's five-lobed petals are another allusion to the "5" in MI5. 

At the bottom of the crest is our motto: "Regnum Defende", meaning "Defend the Realm" in Latin. This refers to a directive issued in 1952 by the then Home Secretary, Sir David Maxwell Fyfe. It defined MI5's mission as being "the Defence of the Realm as a whole" from threats to national security such as espionage, sabotage and subversion

We currently employ more than 5,000 people. Find out more about the people of MI5 on this page.

As an intelligence agency, lots of the work we do is sensitive, therefore, we don't offer public tours of our headquarters.

We have staff based around the UK, and around the world. 

Although MI5 is often described as the UK's "domestic" intelligence service, our operations aren’t purely domestic. Threats to the UK's national security often come from overseas. For instance, foreign intelligence services and terrorists seek to target UK interests at home and abroad. 

We’ll work outside the UK where it’s necessary to protect the UK's national security or to counter security threats to UK interests such as diplomatic premises and staff, UK companies and investments, and our citizens living or travelling abroad. 

Dealing with these threats, wherever they arise, falls within the scope of our functions as set out in the Security Service Act 1989. We work closely with other UK agencies and organisations that are involved in dealing with overseas threats to the UK. We have a close working relationship with our sister UK intelligence agencies, SIS and GCHQ, who are responsible for gathering foreign intelligence. 

We co-ordinate our activity with the Foreign, Commonwealth and Development Office, which provides travel advice on security threats to UK citizens abroad. We also have a number of partnerships with overseas police forces and intelligence agencies.

MI5 isn’t a secret police force and our staff don’t have the power to detain or arrest people. We’re a publicly accountable civilian intelligence organisation, not a law enforcement agency. 

We work closely with the police and other law enforcement agencies to help them bring to justice people who are committing or planning crimes. Most types of intelligence that we produce are capable of being admitted as evidence in criminal trials. The law allows sensitive detail to be withheld where this is in the public interest. 

Our role is defined in law by the Security Service Act 1989. This limits our responsibility to protecting the UK against threats to national security. The law also prohibits us from acting to further the interests of any political party. 

We’re accountable to ministers, Parliament and the courts. Our work is also subject to external scrutiny by specially created oversight bodies, many comprising serving or retired senior judges. Parliament's Intelligence and Security Committee regularly publishes reports on our work.

Yes. The Security Service Act 1989 requires the Director General to produce an annual report for the Prime Minister and the Home Secretary.

The report is not published for security reasons, as it contains sensitive information on the work of MI5. 

However, the Investigatory Powers Commissioner and the Intelligence and Security Committee publish their own reports on MI5's work.

MI5's work has been depicted in a number of films and TV series, notably the BBC's "Spooks" ("MI-5" in the United States). Such works of spy fiction glamorise the world of intelligence and, although they’re entertaining, they tend not to be very realistic. 

We take legal compliance incredibly seriously, which doesn’t always come across in fictitious representations of our work. That said, what is true is that we offer one-of-a-kind careers where you get to do some unique things, working in teams alongside other committed, selfless people who share your determination to make that difference for the sake of our fellow citizens. Not every day is an easy day. But every day counts. 

See Working at MI5 to find out more about what it’s really like to work here.


Yes. MI5 is non-ministerial government department under the authority of the Secretary of State - in practice the Home Secretary. 

Our functions are set out by Parliament in the Security Service Act 1989 and we can only act in the pursuit of those functions. The UK's two other intelligence agencies (SIS and GCHQ) have a similar status, but they’re under the authority of the Foreign Secretary. 

We don’t formulate or implement government policy. We do advise government about the current threats to national security. We also provide advice to government organisations on protective security measures. 

The Security Service Act 1989 requires our Director General to ensure that MI5 is apolitical. The government can’t instruct us to do something for party political reasons. We are operationally independent, which means we cannot be told what or what not to investigate by government.

The Director General receives many invitations to speak at a variety of public events. Pressure on his diary means he has to turn down the vast majority of requests, however, these can be submitted by contacting us.


Terrorism is the biggest national security threat that the UK currently faces. Our highest priority is the threat of international terrorism. Terrorist organisations based in Northern Ireland also continue to pose a serious threat.

Espionage (including cyber espionage) from foreign states is still a significant problem. Despite the end of the Cold War, at least 20 foreign intelligence services are still actively operating against UK interests. Russian and Chinese intelligence activities are an ongoing concern.

The proliferation of weapons of mass destruction (WMD) also continues to pose a threat to international peace and stability. Several countries are actively pursuing WMD programmes and have sought to illicitly obtain equipment and expertise from the UK.

The statutory basis under which MI5 operates authorises us to investigate subversion and serious crime. However, we no longer investigate either of these issues. Subversion is no longer seen as a significant threat and countering serious crime is now the responsibility of the National Crime Agency (NCA).

Terrorism threat levels are kept under review and are published on the threat levels page.

For more information, see the threat levels page.

There are two terrorism threat levels: 

  • the national threat level for the UK which covers all forms of terrorism aside from Northern Ireland-related terrorism in Northern Ireland. This is set by the Joint Terrorism Analysis Centre. 
  • The Northern Ireland-related terrorism in Northern Ireland threat level which is set by MI5. 

There are five ‘levels’ which give a broad indication of the likelihood of an attack. 

  • LOW means an attack is highly unlikely 
  • MODERATE means an attack is possible, but not likely 
  • SUBSTANTIAL means an attack is likely 
  • SEVERE means an attack is highly likely 
  • CRITICAL means an attack is highly likely in the near future

We don’t investigate any group or individual on the grounds of their ethnicity or religious beliefs. MI5 is committed to protecting the security of all of the UK's citizens, of every faith and ethnic group. We only carry out investigations if there is a clear national security reason for doing so.

Some international terrorist groups support an extreme interpretation of Islam that is widely rejected by ordinary Muslims and Islamic scholars. They have been responsible for many terrorist attacks around the world. MI5's largest single area of work is the effort to counter such extremist terrorist groups.

Al Qaida, the Islamic State of Iraq and the Levant (ISIL) and similar groups are often indiscriminate when carrying out attacks. Muslims are often themselves the victims of violence carried out by terrorists who claim to be acting in the name of Islam.

We employ staff of all religions, including Muslims. We are committed to recruiting a diverse range of staff from all backgrounds. This enables us to benefit from their different perspectives and experience. See Languages for information about employment opportunities for British citizens who speak other languages.

MI5 doesn’t have any responsibility for the general vetting of candidates for public sector employment. 

The Security Service Act 1989 imposes strict controls on how we may use or disclose information on individuals. We can only disclose information to assist employment decisions if we do so in accordance with arrangements approved by the Home Secretary. 

The provisions mentioned in the Act mean we play a part in vetting candidates for sensitive government posts. However, our role is confined solely to checking our records. 

If when we check we find that we have a significant and relevant security record on an applicant, we may provide a summary assessment of the security information. However, the mere existence of an MI5 record does not necessarily mean that an assessment will be made. 

There is no "blacklist" and decisions on employing staff are the responsibility of the department concerned. We don’t investigate or interview candidates on their behalf. 

For more information on how vetting is used in government, see HMG Personnel Security Controls.

MI5 does not normally investigate leaks or lost data. The exception is where national security may have been affected as this would form part of our statutory function set out in the Security Service Act 1989. 

MI5 does not have any role in policing the security of government departments. It is the responsibility of each department to ensure that their data is handled securely and that any loss of data is investigated, involving the police if required.

MI5 doesn’t routinely monitor the private lives of prominent people and never simply because of their high profile. We will only carry out an investigation if there’s a clear national security reason for doing so. 

Our investigations are limited by the Security Service Act 1989 to protecting the UK's national security and economic well-being.

MI5 has from time to time been accused of systematically investigating trade unions and pressure groups such as the National Union of Mineworkers and the Campaign for Nuclear Disarmament. 

We have never investigated people simply because they were involved with trade unions or campaigning organisations. The Security Service Act 1989 requires us to be politically neutral and not act for the benefit of any political party. We only investigate matters that affect national security, within the remit set out in the Act. 

In the past, subversion was seen as a significant threat. In a 1975 House of Lords debate, the then Home Office Minister Lord Harris of Greenwich defined subversive activities as those "which threaten the safety or well-being of the state and which are intended to overthrow or undermine parliamentary democracy by political, industrial or violent means." 

As the then Home Secretary Douglas Hurd later put it, "the sole criterion in relation to a subversive threat is whether there is a deliberate intention to undermine parliamentary democracy and whether that presents a real threat to the security of the nation." The Security Service Act 1989 gave this criterion the force of law. 

Some subversive groups sought to infiltrate and manipulate other organisations as a way of exerting political influence. This was a particular concern during the Cold War and before, when there were fears that mainstream organisations were being used as front groups or were being infiltrated by the far left and far right for anti-democratic purposes. 

To meet our responsibility for protecting national security, we investigated individual members of bona fide organisations where there were grounds to believe that a genuine subversive threat existed. We investigated the activities of subversive groups but not the organisations they sought to penetrate. Such investigations were carried out within the laws and processes that applied at the time. 

The threat of subversion is now regarded as negligible and we do not currently carry out investigations in this area. A number of files on historical cases concerning suspected subversive activity have been released to The National Archives, where the public can view them (see MI5 at The National Archives).


Ministers and MPs are not subject to vetting by MI5. 

We’ll tell an incoming Prime Minister about any information we hold on a potential member of the new Cabinet only if that information raises serious national security concerns and only if it appears likely that the individual concerned will need access to sensitive information. 

A similar arrangement has been in operation for the Official Opposition since 1992. The Leader of the Opposition is briefed on any serious security issue concerning a possible member of the Shadow Cabinet. This is necessary because members of the Shadow Cabinet are often briefed on security issues.


An agent, or Covert Human Intelligence Source, is someone who works for us to obtain secret intelligence. They’re one of our most important sources of intelligence. Agents are not employed by MI5 and there is no formal application process to become an agent. 

Agent operations, run strictly in accordance with the relevant legislation, are handled by specially trained MI5 officers. The safety of our agents and their families is always paramount. 

If you know something specific about a threat to national security, we would like to hear from you.

MI5 does not use illegal means to obtain intelligence. 

Our intelligence gathering activities are governed by law and are subject to robust oversight.

An agent or Covert Human Intelligence Source is someone who works with us to obtain secret intelligence. They’re one of our most important sources of intelligence. Agents are not employed by MI5 and there is no formal application process to become an agent. Although our employed members of staff are often erroneously described as "agents", we refer to them as officers. Vacancies are publicly advertised through this website.


Yes. The National Protective Security Authority is part of MI5 and offers expert protective security advice and guidance to businesses and other organisations. Members of the public may also wish to review the advice which forms part of the Action Counters Terrorism information from Counter Terrorism Policing.

Visit the NPSA website

We only investigate individuals whose activities relate to threats to the UK's national security as set out in the Security Service Act 1989. 

Unless you’ve been involved with such a threat it is very unlikely that we’d ever have had any interest in you. 

For more information about accessing records, please visit the managing information page.

If you believe you have been the victim of improper enquiries or other conduct by MI5, you can complain to the Investigatory Powers Tribunal.

If you know something that you think would help us in countering national security threats like terrorism or state threats, please contact us. We cannot help with issues that don’t relate to national security.


Please visit the careers section of the website for frequently asked questions about working for MI5.