The most senior police officer meant to be on duty at Manchester Arena on the night of the explosion missed the attack because he had stopped on the way from the police station, the inquiry has heard.
PC Stephen Corke, a British Transport Police officer who retired seven months after the attack, said it "did not come into my mind" that there might be an attack at the arena that night in May 2017.
All four police officers that were at the arena were standing in the same place, and none were in the City Room foyer, despite instructions to make sure it was patrolled at all times.
They had left the arena unpatrolled for 40 minutes while all took a meal break at the same time, despite instructions to stagger their breaks and finish by 9pm.
PC Corke was not among them because he had decided to check on a "vulnerable location" that was on his way from Greater Manchester Police (GMP) headquarters to Victoria Station, he said.
The location, which he did not specify, was only on the route because a road was being dug up in Ancoats, and he only did a "drive by" check, he added
As a result, the officer was at the wrong end of Deansgate, one of the main shopping streets in Manchester, when the bomb went off and he had to drive at speed down the street to the arena.
His colleague, Matthew Martin, who was the passenger in the car, said they had visited Oxford Road and Deansgate stations to "watch a few trains go in and out."
PC Corke would normally have positioned himself on the mezzanine floor close to where Salman Abedi, the bomber, spent an hour hiding.
He was asked if he had seen Abedi waiting in the City Room with a rucksack on his back, whether he would have realised he was out of place.
"I'd like to think so yes. If it was for a period of time I would agree with you entirely," he said.
Mr Greaney said there were a lot of "ifs and buts in this" but asked, "would you have approached him?"
"There's a good chance of that, yes," the officer said.
But the inquiry heard that PC Corke had spent seven hours dealing with the arrest and interview of a burglary suspect at Greater Manchester Police headquarters at Central Park before heading to Piccadilly Station.
He claimed he had been on hold to the team at the "evidence review gateway" at British Transport Police headquarters in Birmingham for an hour before he could complete the paperwork.
PC Corke said he "scrounged a lift" with another officer who was on duty and chose to "pop into a vulnerable point."
Mr Greaney asked: "You knew the expectation was that you would be back by 10.30pm. May I ask you a very direct question and seek a direct answer, why were you not back by 10.30pm?
"The route we had chosen, we chose to visit a vulnerable point and I mistimed it by a couple of minutes," he said.
The inquiry heard that PC Corke completed the interview by 5.40pm, five hours before the attack, and told his sergeant at 9pm that he would finish the paperwork and take a quick meal break before heading to the arena.
"I was aware that I had to get back to the concert and I thought that I could commit to both within that timescale but unfortunately I mistimed it by a couple of minutes," PC Corke said.
"On the night in question, it did not come into my mind that someone would stoop so low as to do something like that in that location. It was never in the back of my mind.
"We all received various degrees of counter-terrorism briefings but not on that night in question. There was nothing to indicate there was any threat on that evening."
PC Corke said his role was to conduct "a general high visibility patrol showing there are police in the area to all the security staff, the merchandising people and the waiting parents".
He added: "The main thrust of that would be ensuring that the people leave the arena in a safe fashion, getting on the trains and leaving the area."
PC Lewis Brown was a trainee Police Community Support Officer (PCSO) with British Transport Police, at the time being mentored by PCSO Jon Morrey.
He admitted they had both taken an hour and a half meal break in a room at Victoria Station, when the maximum time should have been an hour.
It meant that from 8.58pm to 9.30pm, while Abedi made his way up to the City Room, there were no police officers patrolling the outside of the arena.
PC Brown was asked by Nick de la Poer QC for the inquiry: "Was there any perception that the deployment at Manchester Arena or Victoria Station being an easy option?
"No there was nothing voiced that it was an easy option," he said.
Mr de la Poer asked what his sergeant would have thought if he had turned up and found them all on a meal break.
"I believe the sergeant would have wanted to know why we were on a break for that time, if there was any good reason and would have words of advice with us," the officer said.
"Was there any good reason?" Mr de la Poer asked.
"No, I just think we were on break too long," PC Brown said.
The inquiry continues.