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Looking into Self-Initiated Terrorist (S-IT), who, what, where and why?

What is a Self-Initiated Terrorist (S-IT)?

A Self-Initiated Terrorist is defined as “Person(s) who threaten or mobilise to violence (as defined in Section 1 of the Terrorism Act 2000) without material support or personal direction from a terrorist organisation; but who may still be influenced or encouraged by the rhetoric or ideology of a group”. Self-Initiated Terrorists have previously been referred to as ‘lone actors’.


The threat from Self-Initiated Terrorists (S-IT)

  • Self-Initiated Terrorism currently constitutes the most significant terrorist threat to the United Kingdom.

  • Self-Initiated Terrorism can emerge from any ideology, including Islamist terrorism, Extreme Right Wing Terrorism (ERWT) or Left Wing, Anarchist or Single Issue Terrorism (LASIT).

  • Self-Initiated Terrorists are unpredictable and difficult to detect.

  • Some successful Self-Initiated Terrorists have previously had contact with authorities such as the Police, Prevent, Prison and Probation services or Mental Health services.


Methodologies and targets

Low-Complexity A low-complexity attack and low-sophistication methodology is most likely in the UK, irrespective of ideology. This could include using bladed weapons such as knives.
Crowded Place

Publicly accessible locations and religious institutions are the most likely targets for a Self-Initiated Terrorist attack.

Some Self-Initiated Terrorists are also likely to view authority figures as legitimate targets, such as the Police or representatives of government.


Self-Initiated Terrorist radicalisation

Access to extremist material online is one of the key drivers for Self-Initiated Terrorist self-radicalisation. It is easily accessed by individuals, irrelevant of their ideology. There is a range of terrorist literature, across numerous ideologies, which encourages Self-Initiated Terrorist attacks.

Supporters of terrorist groups continue to leverage armed conflicts overseas for propaganda aimed at inspiring Self-Initiated Terrorist attacks in the West including the UK.


Mental health and Self-Initiated Terrorism

The relationship between Self-Initiated Terrorism, mental health vulnerabilities and neurodiversity is complex. Work is ongoing, across a range of government departments, in order to understand the nature of the relationship between mental health and Self-Initiated Terrorists, and whether this could make an individual more vulnerable to radicalising influences.


Links to prisons

It is likely that perpetrators of future UK SIT attacks, will have previously served a custodial sentence.


Probability and Likelihood in Intelligence assessments

When describing threats in intelligence assessments, Counter Terrorism Policing utilises the Probabilistic Yardstick.

The Probabilistic Yardstick is a tool created by the Professional Head of Intelligence Analysis (PHIA), in the UK government, to standardise the way in which we describe probability in intelligence assessments. For example, if we use the term ‘likely’ what we mean is ‘a 55-75% chance’.

Use the scale below as a reference when reading ProtectUK Insights.


Self-Initiated Terrorists
Attack Methodology
Threat analysis