The materials used on the outside of Grenfell Tower were too combustible for residents to follow the official advice to "stay put" in their flats while they awaited rescue by firefighters, according to expert evidence submitted to the public inquiry into the disaster.
One year on from the fire, which killed 72 people, the inquiry has released four reports into different elements of the structure of the building, which raise serious questions about the role of Kensington and Chelsea council, the arm's-length company that managed the tower, and the string of private companies involved in its refurbishment.
Residents had been told to stay in their flats in the event of a fire – a policy built on the assumption that modern tower blocks can contain a fire in a single flat through building design and the use of fire-retardant materials. Those who survived at Grenfell did so only by ignoring this advice.
Confirming the analysis of several engineering experts, the reports, released on Monday, showed that the fire spread across the building with such speed because of the type of building material used in a 2016 refurbishment – aluminium composite material (ACM) panels – and various other fire safety defects, including the shape of windows.
Barbara Lane, a fire safety engineering expert, said in her report that the building's cladding did not comply with the official regulations on fire safety and failed to combat the spread of fire.
Her report also highlighted more than 100 non-compliant fire doors in the tower and a host of other fire safety failings which were the result of a "culture of non-compliance" from the tower's managers.
"I conclude the entire system could not adequately resist the spread of fire over the walls... The assembly failed adequately to resist the spread of fire to an extent that supported the required Stay Put strategy for this high-rise residential building," she wrote.
Specifically, Lane singled out the building's windows, which had detailing that made it more likely that a fire could break out of a flat and into large cavities in the cladding.
Attempts had been made to minimise this, she said, but "both the horizontal and vertical fire-stopping were installed incorrectly... No evidence has been provided that they were ever tested for performance in an ACP-based Rainscreen cladding system of the type installed at Grenfell."
This and several other factors meant that there was a "disproportionately high risk of fire spread" across the building's cladding.
Lane's report recounts in grim detail how Grenfell residents were trapped in their flats and unable to get past a "hot spot" on the stairs at level 10.
The first call to the London Fire Brigade was at 12:54am and by 1:29am the fire had spread to the 23rd floor. But it wasn't until 2:37am that the order was given to change the "stay put" advice to "everyone out".
At this point, 187 had evacuated; 107 remained inside and 36 of those would escape.
Meanwhile, despite the cause of the fire having been given as a faulty fridge-freezer, there is now some doubt over this.
One expert, Niamh Nic Daeid, wrote that the fire did start in flat 16, on the fourth floor of the block, adding that on the "available evidence, it is more likely than not that the area of origin of the fire was in, or around, the tall fridge freezer in the southeast part of the kitchen."
Such were the fears surrounding the FF175B model of fridge-freezer following the fire, business secretary Greg Clark ordered a review of its safety, which found the product to be safe.
This means that according to leading fire safety experts the true cause of the fire – the most deadly single incident in Britain since the Second World War – is unclear.
This is a developing story. Check back here for updates.