Counter Terrorism Policing is a national network across UK police services set up to prevent and investigate terrorism.

DAC Evans of the Metropolitan Police, speaking at Scotland Yard after taking on the national role this year, warned that the search histories it was reviewing showed “horrific material” which was being accessed “readily and easily online”.

She said this includes violent, misogynistic, and racist content, as well as extreme pornography, material relating to school massacres and “incel“ culture.

This “pick and mix of horror” was sometimes coupled with terrorist material, with a continuing threat from “self-initiated terrorists” radicalised online.

“These sort of grotesque fascinations with violence and harmful views that we’re seeing are increasingly common,” she told reporters.

After the briefing, she told the BBC that technology companies had a responsibility to help counter-terror police “with what access is available to that sort of material”.

A “whole-system approach” was required, she said.

“We have some really deep, dark hot spots – some pockets where we cannot leave the activity and the groups unattended, and we need to continue to maintain our focus on them to keep the threat at bay.”