Dec. 5 (UPI) -- The May terror attack that killed 22 people at an Ariana Grande concert in Manchester could have been prevented by Britain's M15 security service, a report released Tuesday said.
Barrister David Anderson issued a report reviewing the four British terror attacks between March and June. He determined Manchester attacker Salman Abedi had been a "subject of interest" to British authorities and the M15 agency had opportunities to prevent the attack.
"On two separate occasions in the months prior to the attack, intelligence was received by MI5 whose significance was not fully appreciated at the time," the report stated. "It was assessed at the time to relate not to terrorism but to possible non-nefarious activity or to criminality on the part of Salman Abedi. In retrospect, the intelligence can be seen to have been highly relevant to the planned attack."
Anderson said that while M15 had mostly acted properly in response to Abedi, "with the benefit of hindsight" he should've been stopped at the airport when he returned to Britain from Libya.
"It is conceivable that the Manchester attack in particular might have been averted had the cards fallen differently," he said.
Anderson's report stated that three of the six attackers involved in attacks on Westminster, Manchester, London Bridge and Finsbury Park were on M15's radar prior to the attacks which collectively killed 36 people.
Only London Bridge attacker Khuram Butt was actively being investigated by M15 when he and two others drove a van into pedestrians on the bridge before using large knives to attack people in nearby Borough Market.
Home Secretary Amber Rudd said MI5 and counter-terrorism police are running "well over 500 live operations -- a third up since the beginning of the year -- involving roughly 3,000 subjects of interest. In addition, there are over 20,000 further individuals -- or closed subjects of interest -- who have been previously investigated, and may again pose a threat."
Anderson said his report was not intended to "cast or apportion blame. But though investigative actions were for the most part sound, many learning points have emerged."