Police personnel missed Manchester bomber Salman Abedi by “less than a minute” as he prepared for the terror attack in a railway station toilet.
A public inquiry into the 2017 bombing is scrutinising police patrols around Manchester Arena and the neighbouring Victoria station before the explosion.
It previously heard that Abedi had waited in the City Room for an hour before blowing himself up among crowds of Ariana Grande fans leaving a concert.
Hundreds of victims were injured and 22 bystanders killed, including children as young as eight.
Thursday’s hearing was told that just four British Transport Police (BTP) operatives were present on the night, one constable and three voluntary PCSOs.
One pair took a break at around 7.30pm, leaving Manchester Arena as the Grande concert began.
They returned 45 minutes later but did not resume patrolling two hours and 10 minutes after they first departed to buy food, the inquiry heard.
A pair of PCSOs took an hour's break from 9.15pm after conducting a routine check on toilets at Manchester Victoria.
CCTV footage played to the inquiry showed them entering at 8.49pm, seconds after Abedi left with his bomb concealed in a rucksack.
Detective Chief Inspector Sam Pickering, of Greater Manchester Police, said they had missed the terrorist by “substantially less than a minute”.
Abedi, 22, dressed in black and bent over by the weight of the shrapnel packing his home-made bomb in a large rucksack on his back, later made his way to the room connecting the station and arena.
Both police and Showsec security workers received reports of suspicions from members of the public about Abedi, the inquiry was told.
It will examine whether the attack could have been prevented, as well as the response by emergency services and how Abedi was radicalised.
The bomber’s brother, Hashem Abedi, has been jailed for life with a minimum 55 years for his part in the plot.
The inquiry, led by Sir John Saunders, is expected to run into next spring and will continue on Monday.
Additional reporting by PA