Intelligence officers have identified 23,000 jihadist extremists living in Britain as potential terrorist attackers, it emerged yesterday.
The scale of the challenge facing the police and security services was disclosed by Whitehall sources after criticism that multiple opportunities to stop the Manchester bomber had been missed.
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.
Anti-terrorism efforts came under renewed scrutiny when it emerged that Abedi, who murdered 22 people when he detonated a suicide bomb among crowds leaving a pop concert at Manchester Arena on Monday, had been a former subject of interest to MI5.
In a series of fast-moving developments yesterday and today:
● The prime minister downgraded the terror threat from “critical” to “severe” this morning, announcing that soldiers will remain deployed on the streets until Monday
● Assistant Commissioner Mark Rowley, the country’s most senior anti-terrorism police officer, said “significant arrests” meant that a “large part of the network” around Abedi had been wound up.
● Two key properties were identified: a flat in Blackley, north Manchester, where the explosives were made, and a short-term let apartment in the city centre where the device was assembled. Police said that they had “much of the risk contained”.
● It was announced that armed police would patrol some beaches this weekend as the threat level remained critical; there would also be a heavy police presence visible at hundreds of bank holiday events.
● Theresa May made the bombing an election issue by accusing Jeremy Corbyn of blaming British military action overseas for terrorist attacks in the UK. “I want to make one thing very clear to Jeremy Corbyn and to you: it is that there can never, ever be an excuse for terrorism,” she said.
● World leaders at the G7 summit in Sicily called on internet companies to act urgently and “substantially increase their effort to address terrorist content”. The prime minister said she was clear that “corporations can do more”.
Ben Wallace, the security minister, told The Times that the existence of a database of thousands of potential attackers was a stark illustration of the magnitude of the threat. “This reveals the scale of the challenge from terrorism in the 21st century,” he said. “Never has it been more important to invest in intelligence-led policing.”
MI5’s capacity to investigate is limited to about 3,000 individuals at any one time. People are added to and removed from the group of “live” suspects depending on assessments of who poses the greatest risk. When an investigation is closed, the people identified drop into a growing group whose risk is seen as reduced.
Sources say that the pool of “former subjects of interest” has swollen to 20,000 during the years of Islamist threat since 2001.
There is concern that the intelligence agencies have been poor at detecting former subjects of interest who return to extremism.
The two men who murdered Fusilier Lee Rigby in 2013 had been known to the agencies but had dropped down the priority list and their continued adherence to violent extremism was missed. 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.
Raffaello Pantucci, director of international security studies at the Royal United Services Institute, said that the figures were “disturbing but not surprising”. He added: “For many of these people, the jihadist ideology never leaves them — it is very deeply ingrained.”
Anthony Glees, head of security and intelligence studies at the University of Buckingham, said: “To have 23,000 potential killers in our midst is horrifying. We should double the size of MI5, as we did in World War Two, and expand the number of intelligence-led police by thousands. We can’t go on as if this wasn’t happening.” Last night Ariana Grande, the American singer whose concert was targeted by Abedi, said she planned to return to Manchester to stage a benefit concert for the victims. Liam Gallagher will donate profits from his first solo gig next week to victims.
This article has been edited to remove a reference to the flat being rented through Airbnb, which was incorrect