MI5 boss Ken McCallum has said he is "profoundly sorry" and "deeply regrets" the security service's failure to prevent the Manchester Arena Bombing atrocity.
In an unprecedented move, the security service has issued an apology for its failure to stop the attack, which saw Salman Abedi detonate his homemade device at the end of an Ariana Grande concert in May 2017.
The explosion killed 22 people and injured hundreds more and remains the deadliest terror attack in Britain since 7/7.
Manchester Arena Inquiry chairman Sir John Saunders released his findings on Thursday, which found MI5 officers failed to take appropriate action on two key pieces of intelligence received in the months before the attack.
MI5 Director General Ken McCallum issued a statement in response to the report on Thursday afternoon, following the publication of the third volume of the Manchester Arena Inquiry's report.
"The terrorist attack at the Manchester Arena was a terrible tragedy," it read. "The bomber killed 22 innocent people and harmed many others.
"My thoughts are with the families and friends of those killed, and with all those whose lives were changed by this appalling act of terrorism.
"Having examined all the evidence, the Chair of the Inquiry has found that “there was a realistic possibility that actionable intelligence could have been obtained which might have led to actions preventing the attack.”
"I deeply regret that such intelligence was not obtained. Gathering covert intelligence is difficult – but had we managed to seize the slim chance we had, those impacted might not have experienced such appalling loss and trauma.
"I am profoundly sorry that MI5 did not prevent the attack. The people of MI5 and our policing partners come to work every day to stop terrorism.
"We continually work to improve the counter-terrorism system; since the terrible events of 2017 we have made more than 100 improvements. But we are determined to do more.
"As the Chair now considers his recommendations, we will engage fully. Where there are opportunities to strengthen the UK’s defences further, MI5 will act.
"We will continue to do everything in our power to keep our country safe from hidden threats. MI5 exists to stop atrocities.
"To all those whose lives were forever changed on that awful night: I am so sorry that MI5 did not prevent the attack at the Manchester Arena."
The Manchester Arena Inquiry's report published Thursday morning revealed that 22-year-old Abedi, of Libyan descent, was likely helped by other plotters who have never been caught.
Sir John, who led the probe, found he may have smuggled a detonator switch into the UK after MI5 officers failed to take appropriate action on two key pieces of intelligence received in the months before the attack.
He concluded: "There was a significant missed opportunity to take action that might have prevented the attack.
"It is not possible to reach any conclusion on the balance of probabilities or to any other evidential standard as to whether the attack would have been prevented.
- There were two key pieces of intelligence received in the months before the attack
- An MI5 officer 'Witness C' failed to immediately report to colleagues after concluding intelligence may have been of 'pressing national concern'
- Abedi may have smuggled a detonator switch into the UK after it was found to have been manufactured in Romania and supplied to Libya
- Abedi was not stopped and searched under terror laws when he returned to the UK as MI5 could have followed the Nissan Micra he used to store explosives
- Abedi probably had help from others in plotting the attack
- Abedi's brothers, family and mother held extremist views
- Convicted terrorist Abdalraouf Abdallah played a key role in radicalising Abedi
"However, there was a realistic possibility that actionable intelligence could have been obtained which might have led to actions preventing the attack.
"The reasons for this significant missed opportunity included a failure by a Security Services officer to act swiftly enough."
The report was critical of a female MI5 officer, known as "Witness C", who concluded that the second piece of intelligence might have been of "pressing national security concern".
But she did not immediately discuss it with colleagues or write up a report that day, Sir John found.
"The delay in providing the report led to the missing of an opportunity to take potentially important investigative action," he concluded.
Abedi was in Libya at the time the information came in but was able to enter the UK four days before the attack without being stopped. The report said that had adequate action been taken, his return would have been taken "extremely seriously".
A Sistema 45910 switch used to detonate the bomb was manufactured in Romania and supplied to Libya.
Sir John found there was a "possibility" that it was obtained by Abedi while he was in the country and that he had it on him when he passed back through Manchester airport on May 18.
Had adequate action been taken, he might have been stopped and searched under terror laws and MI5 could have followed the Nissan Micra he used to store the explosive, Sir John found.
The report stated: "We cannot know what would have happened, but there is at least the material possibility that opportunities to intervene were missed."
Sir John concluded that other suspects linked to Abedi, who have never been charged, probably helped him launch the attack.
Sir John examined how the brothers were radicalised and concluded that their father Ramadan Abedi, mother Samia Tabbal and elder brother Ismail Abedi, all held extremist views.
"Their views influenced the development of SA’s and HA’s worldviews. It is also likely that SA and HA fed off each other’s ideas and radicalised each other," Sir John concluded.
He found convicted terrorist Abdalraouf Abdallah, who was a close friend of the bomber, played an "important role" in radicalising Abedi along with Raphael Hostey who was killed in Syria in 2016 while fighting for Islamic State.
The report also emphasised the challenges facing the security services, with 37 late-stage terror plots had been foiled since 2017
Evidence into the circumstances leading up to and surrounding the atrocity was heard in Manchester between September 7 2020 and February 15 2022.
