On May 26, four days after the major terrorist attack on an Ariana Grande concert in Manchester, British intelligence officials stated that they had identified 23,000 jihadist extremists living in the UK, all of them considered potential terrorist attackers. According to The Times,
About 3,000 people from the total group are judged to pose a threat and are under investigation or active monitoring in 500 operations being run by police and intelligence services. The 20,000 others have featured in previous inquiries and are categorised as posing a “residual risk”.
The two terrorists who have struck in Britain this year — Salman Abedi, the Manchester bomber, and Khalid Masood, the Westminster killer — were in the pool of “former subjects of interest” and no longer subject to any surveillance.
The report adds that the two men who beheaded British soldier Lee Rigby in London, in 2013, had been known to the security services, just as Abedi and Masood were, but had been dropped to low priority.
David Anderson, QC, the former reviewer of anti-terrorism laws, noted concerns in his 2015 report about the “speed with which things can change” around suspects and “the difficulties in knowing how best to prioritise limited surveillance resources”. Senior police have also spoken of the difficulty in identifying the triggers that might “reactivate” extremist behaviour.
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