A major report into the Manchester Arena terror attack states it cannot say if a two-hour delay in deploying firefighters might have saved lives.
The fire service was effectively "outside of the loop" of police and ambulance emergency responders so firefighters, some who heard the bomb go off, and trained in first-aid and terror scenarios with specialist equipment, did not get permission to go to the scene until hours after the suicide bombing, despite being stationed half a mile away.
"Strategic oversights" by police commanders led to confusion over whether an "active shooter" was on the loose and poor communications between Greater Manchester Police (GMP) and Greater Manchester Fire and Rescue Service (GMFRS) meant fire crews only arrived two hours and six minutes after the bombing, which left 22 dead and scores injured.
Among those killed were 14-year-old Sorrell Leczkowski, a pupil at Allerton High School in Leeds, Leeds Beckett University student Courtney Boyle, 19, and Wendy Fawell, 50, from Otley.
The 226-page report by Lord Bob Kerslake was commissioned by Andy Burnham, the mayor of Greater Manchester, to assess the preparedness and emergency response to the attack last year.
The report, released on Tuesday, makes 50 recommendations but states its panel of experts was not to answer the question of, "would the earlier arrival of GMFRS at the scene have made any difference to the medical outcomes of the injured?"
"This is a question that only the coronial inquests can decide," the report said.
But it says firefighters "would have been much better placed to support and, potentially, to accelerate the evacuation of casualties from the foyer," if they had gone to the scene.
Suicide bomber Salman Abedi detonated his home-made device at 10.31pm on May 22 last year, as 14,000 people streamed out of Manchester Arena at the end of an Ariana Grande concert.
Officers from British Transport Police were on scene one minute later and declared a major incident by 10.39pm.
The police duty inspector in the GMP force control room declared Operation Plato, a pre-arranged plan when it is suspected a marauding armed terrorist may be on the loose - and assumed, wrongly, other agencies were aware.
But he was praised for taking one of the most crucial "life or death" decisions of the night, a "key use of discretion" to override the rules and allow paramedics and police to continue treating the injured even though they may be in danger of further attacks.
But GMFRS and the North West Ambulance Service (NWAS) were only informed an hour and a half later and by then Operation Plato was effectively put on "stand by" as it emerged the attack was from a single suicide bomber and not the prelude to further armed attacks.
Armed police and 12 ambulances were on the scene within 20 minutes but a shortage of stretchers hampered ferrying the injured from the foyer to a casualty area on the station concourse.
The senior fire officer on duty, a National Inter-Agency Liaison Officer, stuck to rules which dictate keeping emergency responders 500 metres away from any suspected "hot" zone of danger from a potential armed terrorist.
It was "fortuitous" the NWAS were not informed - otherwise they may have pulled out their paramedics, the report stated and instead they stayed and "lives were saved".
As the fire officer could not get through on the phone to the police force duty officer, the response of the fire service was "brought to the point of paralysis" to the "immense frustration on the firefighters faces".
Instead of rushing to the scene to help, fire crews and a Special Response Team, trained to deal with terrorist incidents, rendezvoused at fire station outside the city centre.
And while a joint strategic co-ordinating group of emergency response services and others gathered at GMP HQ in east Manchester, GMFRS chief fire officer Peter O'Reilly, who has now retired, focused his senior officers at their own HQ in Salford, which played a "key role" in delaying the response further.
The report says it hopes, in future, different services control rooms not being able to properly pass critical information between them "will never happen again."
Lord Kerslake, the panel, police, fire and other authority bosses will shortly hold a press conference about the report's findings.