UK Threat Levels

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The UK Threat Levels are the alert states that have been in use since 1 August 2006 by the British government to warn of forms of terrorist activity. Before then a colour-based alert scheme known as BIKINI state was used.[1] The response indicates how government departments and agencies and their staffs should react to each threat level.

Current threat level[edit]

The current level, as from 27th May 2017, is Severe. The previous threat level was Critical following the Manchester Arena bombing of 22 May 2017.[2]

Categories of threat[edit]

Since 24 September 2010, the Home Office has reported three different categories of terrorist threat:[3][4]

  • Threat from international terrorism.
  • Terrorism threat related to Northern Ireland in Northern Ireland itself.
  • Terrorism threat related to Northern Ireland in Great Britain (i.e. excluding Northern Ireland).

A fourth category of terrorist threat is also assessed but is not disclosed, relating to threats to sectors of the UK's Critical National Infrastructure such as the London Underground, National Rail network and power stations.[5]

The Joint Terrorism Analysis Centre (JTAC) is responsible for setting the threat level from international terrorism and the Security Service (MI5) is responsible for setting both threat levels related to Northern Ireland.[6] The threat level informs decisions on protective security measures taken by public bodies, the police and the transport sector.[7]

Threat levels[edit]

Threat level Response
Critical An attack is expected imminently.
Maximum protective security measures to meet specific threats and to minimise vulnerability and risk. Critical may also be used if a nuclear attack is expected.
Severe An attack is highly likely.
Additional and sustainable protective security measures reflecting the broad nature of the threat combined with specific business and geographical vulnerabilities and judgements on acceptable risk.
Substantial An attack is a strong possibility.
Moderate An attack is possible, but not likely.
Routine protective security measures appropriate to the business concerned.
Low An attack is very unlikely.


Threat levels were originally produced by MI5's Counter-Terrorism Analysis Centre for internal use within the British government. Assessments known as Security Service Threat Reports or Security Service Reports were issued to assess the level of threat to British interests in a given country or region. They had six levels: Imminent, High, Significant, Moderate, Low and Negligible. Following terrorist attacks in Indonesia in 2002, the system was criticised by the Intelligence and Security Committee of Parliament (ISC) as insufficiently clear and needing to be of greater use to "customer departments".[8]

The 7 July 2005 London bombings prompted the government to update the threat level system following a recommendation from the ISC that it should deliver "a greater transparency of the threat level and alert systems as a whole, and in particular [it is recommended] that more thought is given to what is put in the public domain about the level of threat and required level of alert." The system was accordingly simplified and made easier to understand.[9] Since 2006, MI5 and the Home Office have published international terrorism threat levels for the entire UK on their websites, and since 2010 they have also published threat levels for Northern Ireland, with separate threat levels for Northern Ireland and the rest of the UK.[6]

Changes to threat levels[edit]

Graph showing the changes in threat levels between 2006 and today

The following table records changes to the threat levels since August 2006:[6]

Date Threat level
1 August 2006 Severe
10 August 2006 Critical
13 August 2006 Severe
30 June 2007 Critical
4 July 2007 Severe
20 July 2009 Substantial
22 January 2010 Severe
11 July 2011 Substantial
29 August 2014 Severe
23 May 2017 Critical
27 May 2017 Severe
Date International terrorism Northern Ireland related terrorism
24 September 2010 Severe GB: substantial NI: severe
11 July 2011 Substantial GB: substantial NI: severe
24 October 2012 Substantial GB: moderate NI: severe
29 August 2014 – 10 May 2016 Severe GB: moderate NI: severe
11 May 2016 – 22 May 2017 Severe GB: substantial NI: severe
23 May 2017 - 26 May 2017 Critical GB: substantial NI: severe
27 May 2017 - current Severe GB: substantial NI: severe

See also[edit]


  1. ^ Threat Levels, July 2006
  2. ^ "UK threat level raised to highest level". BBC News. 2017-05-23. Retrieved 2017-05-23. 
  3. ^ "Irish terror attack a 'strong possibility'". BBC News. 25 September 2010. Retrieved 20 December 2010. 
  4. ^ "Press Release: Increased risk of Irish-related terrorism". United Kingdom Home Office. 24 September 2010. Retrieved 20 December 2010. 
  5. ^ Bunkall, Alistair (4 June 2016). "Was it a mistake to lower the UK terror threat before London Bridge attack?". Sky News. Retrieved 4 June 2016. 
  6. ^ a b c "Threat levels". MI5. Retrieved 1 April 2017. 
  7. ^ Foley, Frank (2013). Countering Terrorism in Britain and France: Institutions, Norms and the Shadow of the Past. Cambridge University Press. p. 166. ISBN 978-1-107-02969-9. 
  8. ^ Hennessey, Thomas; Thomas, Claire (2011). Spooks the Unofficial History of MI5 From the First Atom Spy to 7/7 1945-2009. Amberley Publishing Limited. pp. 228–9. ISBN 978-1-4456-0801-3. 
  9. ^ Staniforth, Andrew; Sampson, Fraser (2012). The Routledge Companion to UK Counter-Terrorism. Routledge. p. 276. ISBN 978-1-136-25430-7. 

External links[edit]