Britain's MI5 security service missed “significant” opportunities which may have prevented a deadly suicide bombing at the end of a concert in Manchester, an inquiry into the attack concluded on Thursday. That included a “failure” by an officer of the domestic counter-intelligence and security agency to act fast enough once information came in that could have led to bomber Salman Abedi being interrogated days before he carried out the attack, or led to the discovery of explosives hidden in his car. The nature of that intelligence was not disclosed. Chairman Sir John Saunders said it was “risky” for the security services to focus on the terrorism threat from ISIS in Syria at the time and ignore the danger posed by groups in Libya in 2017. Abedi, who had connections to ISIS and Al Qaeda terrorists and fought alongside extremists in Libya, frequently come on the radar of security services and counter-terrorism police. Sir John also found that Abedi, who was from Manchester but of Libyan descent, probably received help to plot the attack from someone in Libya and said his family bore “significant responsibility” for his extreme views. His radicalisation was driven by “noxious absences and malign presences”, he said. Inspired by ISIS group, Abedi blew himself up amid crowds of mostly young people who had been attending the concert by American pop star Ariana Grande. Twenty-two people were killed — the youngest aged only eight — and hundreds were injured in the explosion on May 22, 2017, as parents collected their children at the Manchester Arena. “There was a significant missed opportunity to take action that might have prevented the attack,” Sir John said in his third and final report on the bombing, the deadliest in Britain since the 2005 London transport attacks. “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.” Summarising his findings before bereaved families gathered at Manchester Hall, and referring to the failure of an officer to immediately write up a report on one of the pieces of intelligence, he said: “Based on everything the [MI5] Security Service knew or should have known, I am satisfied that such an investigative action would have been a proportionate and justified step to take. “There was a realistic possibility that actionable intelligence could have been obtained which might have led to actions preventing the attack.” MI5 Director General Ken McCallum said he was “profoundly sorry that MI5 did not prevent the attack” and added: “I deeply regret that such intelligence was not obtained.” Abedi’s brother, Hashem Abedi, 25, was jailed for life after he was convicted of assisting in the plot. His older brother, Ismail Abedi, to the “horror” of relatives of those murdered, was allowed to flee the UK, avoiding being called as a witness. Referring to Abedi's radicalisation, Sir John said: “I have concluded that there were a number of contributory factors to Salman Abedi's radicalisation. “His family background and his parents' extremist views, along with their participation in the struggle in Libya, played a significant part. “That struggle involved people who were radical violent extremists. During the time Salman Abedi and Hashem Abedi spent in Libya, during which they were probably involved in fighting. They are likely to have come into contact with a number of violent extremists. “It is likely that those extremists included members of the Islamic State who would be in a position to provide the brothers with expertise in the making of bombs and in carrying out counter surveillance measures.” Sir John said he was not able to obtain a complete picture of the part the Abedis' family played in their radicalisation nor of what happened while they were in Libya. “That is because other members of the family, namely their parents and brother, were not willing to give evidence to the inquiry,” he said. “Salman and Hashem's parents were invited to provide statements but declined to do so. As they are currently out of the jurisdiction, there were no further steps that I could take. “Ismail Abedi, who was in the country at the time I requested a statement, managed to leave the UK so that he didn't have to provide information which he was in a position to give. “Whether [or not], if I had succeeded in getting Ismail Abedi into the witness box, he would have assisted the inquiry is very doubtful.” But while their family hold “significant responsibility” for the brothers’ radicalisation, there is “insufficient evidence” any of them had specific knowledge an attack was being planned, the report states. He said Didsbury Mosque, which Abedi attended on occasion, was not to blame, although it has not been completely open. Sir John said: “I consider it unlikely … that Salman Abedi was radicalised at the Didsbury Mosque but some of the evidence given on behalf of the mosque about the association of the Abedi family with the mosque was unsatisfactory. “It looked as if the Didsbury Mosque was trying to distance itself from the Abedi in a way which I did not accept was accurate.” Outside their family, the Abedi brothers were also subject to malign influences, the report concluded. Some of Salman’s friends were involved in drug dealing and crime, leaving him with “almost no close connections or friendships that would tie him to law-abiding society”, the report said. Richard Scorer, principal lawyer at Slater and Gordon, who represented 11 of the families at the inquiry, said: “Today's report has been deeply painful to read, but also eye opening. “On the issue of the preventability of this attack, inevitably the report provides less information than we would have wanted. “But it is now very clear that there was a failure to properly assess key intelligence about Salman Abedi — a failure to put it into proper context, and, most catastrophic of all, a delay in acting on it. “As a result of these failures, at the very least, a real possibility of preventing this attack was lost. This is a devastating conclusion for us. “The failures exposed in this report are unacceptable. “The public are entitled to expect that information of national security importance will be acted on speedily and, crucially, that the system will ensure that this happens. It must do so in the future.” Sir John said he had looked in detail at the “various occasions” when Abedi could have been referred to Prevent, the UK counter-terror programme. “I have concluded that he should have been,” he said. “I heard evidence that his referral was considered at one stage but he was not considered suitable. “There can be no guarantee that Salman Abedi or Hashem Abedi would have agreed to participate in the Prevent programme. “I have concluded that there was at least a period during Salman Abedi's journey to violent extremism when he should have been referred. “It is very hard to say what might then have happened.” Mr Scorer said it is “clear that Salman Abedi should have been referred to Prevent”. “It is clear that the education system needs to be more vigilant in picking up signs of radicalisation. It is clear that Didsbury Mosque turned a blind eye to extremism in its midst. “Sir John's report today contains many lessons; we must heed every one of them and make the necessary changes urgently.” Speaking outside, Caroline Curry, mother of victim Liam Curry, said the families had not previously received any acknowledgement of failures. “All we, as families, have asked for from day one is the truth, acknowledgement of failures and a determination to make sure that those failures are fixed,” she said. “So that next time, because there will be a next time, but hopefully next time there won’t be as many families going through the utter heartbreak we have had to endure for the last five years, nine months, one week and one day. “We didn’t get that acknowledgement from anyone other than GMFRS [Greater Manchester Fire and Rescue Service], until the chairman’s reports were published. “Shame on you all.” Thursday’s third and final report into the terror attack followed two earlier reports. The first was issued in June 2021 and highlighted a string of “missed opportunities” to identify Abedi as a threat before he walked across the City Room foyer and detonated his shrapnel-laden device. Sir John’s second report last November delivered scathing criticism of the emergency services response to the bombing. Security minister Tom Tugendhat said the government, security services and emergency services were wholly committed to “learning the lessons of this unspeakable tragedy”, while Home Secretary Suella Braverman said: “I am committed to working with MI5, policing and partners to study the recommendations. Together we will do everything possible to prevent a repeat of this horrifying attack.”