MI5 did not act quickly enough on key information and missed a significant opportunity to prevent the suicide bombing that killed 22 people at an Ariana Grande concert in Manchester in 2017, a public inquiry concluded this Thursday.

Judge John Saunders, who led the inquiry into the Manchester Arena attack, said an MI5 officer admitted they considered intelligence about suicide bomber Salman Abedi which suggested he could be a potential national security problem, but did not discuss it with colleagues quickly enough.

In a rare televised statement, MI5 director-general Ken McCallum, who normally keeps a low public profile, said he was “deeply sorry that MI5 did not prevent the attack.”

“Gathering secret intelligence is difficult, but had we been able to seize the little chance we had, those affected might not have experienced such terrible loss and trauma,” McCallum said.

Abedi, 22, detonated a backpack bomb in the arena’s foyer as thousands of young fans, including many children, left the pop star’s show. More than 100 people were injured. Abedi died in the explosion.

His brother, Hashem Abedi, was convicted in 2020 of helping to plan and carry out the attack. He was sentenced to life imprisonment.

Saunders said that if MI5 had acted on the intelligence it received, it could have led to action – including possibly stopping Abedi at Manchester Airport when he returned from Libya four days before the attack or following him to his car on the day of the attack.

Caroline Curry, whose 19-year-old son Liam Curry was among those killed in the bombing, said Thursday she could not forgive intelligence officials for their failures. “From top to bottom, MI5 to the associates of the attacker, we will always believe that you all played a part in the murder of our children,” she told reporters.

Abedi had been a “subject of interest” to MI5 officers in 2014, but his case was closed soon after because he was considered low risk. Saunders also said authorities failed to refer Abedi to the government’s anti-terrorism program, known as Prevent. Thursday’s report was the third and final in the attack.