‘Extremism’ is used within Special Branch to describe the activities of those it is targeting. It is often used alongside ‘militancy’, ‘subversion’ and ‘terrorism’, depending on context. A precise definition is not given in the Special Branch Guidelines, and the word itself is somewhat circular - extremism is the politics of an extremist, whose activities or beliefs are considered extreme, i.e. what ‘most people’ would not think normal, reasonable or acceptable. This naturally creates a considerable latitude in how it is used within policing.
Within Special Demonstration Squad-related documents, it appears to be used to refer to anyone not relatively close to the centre of the political spectrum, usually those who had different perspectives on how democracy should be organised (or done away with). This covered a broad swathe of political beliefs and Special Branch applied it equally to them all, regardless of their propensity for or advocacy of violence: anyone seeking social change could find themselves characterised by it.
Initially, it was applied by Special Branch to the political left and right wings and Irish republicanism, often being used in the acronym XLW - Extreme Left Wing and XRW - Extreme Right Wing.
Extreme Left Wing covered a wide variety of political traditions, whether Trotskyist, Maoist, revolutionary Marxist/communist, socialist and/or anarchist. It also covered those groups willing to engage in civil disobedience or take direct action, such as the peace movement, anti-racist/ anti-Apartheid groups, or Black Power/liberation groups.
Later, animal rights activists were labelled as AREs - Animal Rights Extremists. This was further extended to cover environmentalists (though eco-terrorism is also used in this context).
Within the Metropolitan Police Special Branch, these groups were initially monitored by B Squad, changing to C Squad from 1969 onwards.
In the 2000s the term ‘Domestic Extremism’ appears to have been adopted, though without a clear definition, finding its way into the names of various units and positions.
Initially it was focused on animal rights, but was soon adopted to cover left and right wing and environmentalist activities alike.
In 2009, a working definition was reported to include individuals or groups:
that carry out criminal acts of direct action in furtherance of a campaign. These people and activities usually seek to prevent something from happening or to change legislation or domestic policy, but attempt to do so outside of the normal democratic process.
It came in for criticism because such a broad definition meant anyone in such a group could be considered an extremist even if they had no intention of committing any crime. It effectively treated many forms of lawful protest as criminal acts, and thus justified surveillance of people and campaigns.
It is still used within policing structures but has been partially replaced by ‘aggravated activism’.