A senior police officer agreed his force “let the public down”, the inquiry into the Manchester Arena bombing heard.
But Assistant Chief Constable Sean O’Callaghan, of British Transport Police (BTP), said he agreed with the overall BTP risk assessment of an attack or violence on the night of the Ariana Grande concert as “low”.
Mr O’Callaghan, who was himself not serving with BTP at the time of the attack, said: “In relation to the information available I understand why that assessment was made.”
Manchester-born suicide bomber Salman Abedi detonated his homemade rucksack bomb in the foyer of the arena, known as the City Room, at the end of the gig, murdering 22 bystanders and injuring hundreds more on May 22, 2017.
The inquiry heard the BTP deployment on the night, comprised of one BTP officer who was still on probation and just eight months into the job and three PCSOs, was based on security and safety risk assessment concerned with crowd control and young people becoming separated from accompanying adults.
The “profile” for the 14,000 person crowd was for teenage girls and their parents with no fears over gang violence and crowd trouble.
Paul Greaney QC, counsel to the inquiry, said: “But there is of course another potential source of violence, which is a hostile actor. A terrorist.”
Mr O’Callaghan said there had been no previous attacks on the arena, no terror attacks on entertainment venues in the UK to that date and no specific intelligence on a possible terror attack.
But Mr Greaney pointed out the overall terror threat for the UK was “severe”, meaning an attack was “highly likely” to occur. And he pointed out the deadly attacks in Paris on the Bataclan music venue in Paris and Stade de France in November 2015 and an attempted attack at an outdoor concert in Germany the previous year.
Mr O’Callaghan said the threat level had been “severe” for the previous two years and nine months and was at the same level for the previous Ariana Grande concert there in 2015.
He said the only suicide bomb attack in the UK had been 12 years previously.
He added: “Terrorism is in the officers’ minds of every police officer in the country and every BTP officer going about their business, whether on duty or off duty.
“I don’t believe for one minute that consideration wasn’t in the officers’ minds.”
Mr Greaney listed issues which “might be concluded went wrong” on the night of the attack. They included having only four officers on duty, the Pc and her PCSO colleague taking a two-hour lunch break, with no officers on duty at the time Abedi made his “final approach” to take up position in the City Room for the end of the concert.
And there was no police officer in the room for the end of the gig as dictated by the Police Sergeant’s instructions.
Mr Greaney continued: “I’m going to ask you a blunt question, which is, is it fair to say on the 22nd May, 2017, before the attack, BTP let the public down in their policing of the City Room?”
The witness replied: “The attack that happened that night, certainly happened on our watch, yes.
“It was our responsibility to police that arena and that attack happened when we was policing it and there were police officers deployed or planned to be deployed to the site of the attack and they were not there.
“So, in that term, yes.”
The inquiry is looking at circumstances before, during and after the attack.
The hearing continues.