MI5 was “actively” investigating the ringleader of the London Bridge atrocity at the time of the rampage, while the Manchester bombing could have been stopped “had the cards fallen differently”, an official assessment has found.
It confirms that three terrorists involved in attacks that hit Britain between March and June this year had at some point been on authorities’ radar.
The UK’s security apparatus faced questions after dozens of victims were killed or injured in Westminster, Manchester, London Bridge and Finsbury Park.
MI5 and police launched independent reviews to examine what was known about the perpetrators before they struck and decisions made on intelligence.
An independent assessment of the findings by David Anderson QC concludes that there is “no cause for despair”, saying most attacks continue to be successfully disrupted.
But he notes that, other than in the case of Finsbury Park, it cannot be said that MI5 and police were “entirely blindsided”.
The report says: “Khalid Masood (Westminster) and Salman Abedi (Manchester) had both been subjects of interest, and Khuram Butt (London Bridge) remained under active investigation.
“Substantial and appropriate coverage was in place around key individuals, and mechanisms designed to assess risk were working as intended.
“MI5 and counter-terrorism policing got a great deal right; particularly in the case of Manchester, they could have succeeded had the cards fallen differently.”
In response to the findings, Home Secretary Amber Rudd said the blame for the attacks “lies squarely” with the terrorists.
Abedi was not under active investigation when he detonated a suicide device at Manchester Arena in May.
But Mr Anderson’s review says that MI5 came by unspecified intelligence in the months before the attack which, “had its true significance been properly understood”, would have caused an investigation into him to be opened.
The report says: “It is unknowable whether such an investigation would have allowed Abedi’s plans to be pre-empted and thwarted. MI5 assesses that it would not.”
Abedi was also identified by a separate “data-washing exercise” as falling within a small number of former subjects of interest who merited further consideration.
Salman Abedi on the night he carried out the Manchester Arena terror attack (Greater Manchester Police/PA)
However, a meeting scheduled to consider the results of this process had not been held at the time of the bombing, in which 22 people were killed.
An opportunity was also missed to place Abedi on “ports action” after he travelled to Libya in April.
The report says: “It is conceivable that the Manchester attack … might have been averted had the cards fallen differently:
Westminster attacker Masood was known to police and MI5 for association with extremists but he was a “closed” subject of interest at the time of the atrocity in March.
The arrest of Khalid Masood (Stefan Rousseau/PA)
Intelligence officers and police had no reason to anticipate his murderous actions, according to the report.
It also reveals how, in the days prior to his attack, Masood conducted reconnaissance of Westminster Bridge in person and online, and browsed YouTube for videos relating to terrorism.
Minutes before he struck, the terrorist shared a “Jihad document” with numerous WhatsApp contacts.
Butt, who led the three-strong gang behind the London Bridge van and knife attack in June, was the principal subject of an MI5 investigation from mid-2015 until the date of the deadly assault.
The report says material relating to Butt received in the two weeks prior to the attack added little to the intelligence picture and did not identify activity that led up to it.
Another of the London Bridge gang, Youssef Zaghba, was placed on an EU warning list in March last year.
Police and MI5 have foiled nine plots since the Westminster attack in March (Victoria Jones/PA)
However, Italian authorities placed him on the database under a marker identifying him as being subject to checks for serious crime rather than one which would have led to him being automatically identified as a national security risk.
It was also revealed that, in June 2016, MI5 received an inquiry from Italian authorities about Zaghba but the agency has no record of responding – “noting by way of possible explanation that it arrived in the incorrect mailbox”.
The request was not chased up by Italian officials.
“The story is not a happy one, but, as MI5 points out, even if the request had been actioned, it would have resulted in a nil return,” the report adds.
Zaghba, and the third London Bridge attacker, Rachid Redouane, were never investigated by MI5.
In the fourth incident covered by the review, one man died after a van crashed into a group near the Finsbury Park mosque in north London in June.
Darren Osborne, 48, from Cardiff, has been charged with murder.
Mr Anderson’s report says police had no intelligence to suggest Osborne was going to commit the alleged attack, while MI5 held no intelligence on him.