A new official report looking at how security agencies handled terror attacks in Britain this year revealed that the Manchester bombing could have been avoided if information about the bomber had been handled differently.

Lawyer David Anderson undertook the report, appointed by Amber Rudd, secretary of the Home Department. The report looked at how Britain’s top security agency, MI5, and police, handled the four terror attacks in Britain between March and June of this year. Anderson’s report piggybacked on internal reviews several law enforcement agencies had already conducted.

Salman Abedi was the suicide bomber responsible for the May 22 attack after an Ariana Grande concert at Manchester Arena. The attack killed 23 people and injured more than 500.

Abedi was investigated twice before the attack, but his case had been closed each time. Law enforcement had become aware of new information about Abedi months before the attack, but the “significance was not fully appreciated at the time,” and the investigations were dropped.

The report said that “in retrospect, the intelligence can be seen to have been highly relevant to the planned attack.”

The report also looked at two other terrorists who had already been investigated before their attacks. Khalid Masood was investigated before he undertook a March 22 attack on and around Westminster Bridge. He killed five and injured more than 50, first by slamming a van into a crowd before getting out and stabbing a police officer.

“With the benefit of hindsight, intelligence was misinterpreted in 2017,” said Anderson.

Khuram Butt was under active investigation by MI5 when he along with three others killed 8 and injured 48 in a June 3 London Bridge attack.

“[The investigation] continued to varying degrees until the day of the attack, it did not reveal the plans or Khuram Butt and his two co-conspirators,” read the report.

Butt had been investigated for two years.

“It is not the purpose of the internal reviews, or of this report, to cast or apportion blame. But though investigative actions were for the most part sound, many learning points have emerged,” said Anderson. “It is conceivable that the Manchester attacks, in particular, might have been averted had the cards fallen differently.”

MI5 had plans to revaluate Abedi as a person of interest, but the Manchester attack took place before he was reexamined.

Anderson said that MI5 was able to prevent nine terror attacks in Britain this year, and 22 since 2013, but that improvements outlined in the internal reports needed to happen.

“MI5 and the police have identified the need to use data more effectively, to share knowledge more widely, to improve their own collaboration and to assess and investigate terrorist threats on a uniform basis,” said Anderson. “No free society can offer immunity from terrorism, or any other kind of crime.”

Manchester blast Police vehicles are seen outside the Manchester Arena, where U.S. singer Ariana Grande had been performing in Manchester, northern England, May 23, 2017. Photo: Reuters/Jon Super