Blow-by-blow footage of Grenfell Tower being devoured by flames has been shown to the public inquiry during a horrifying account of the inferno’s spread.
Professor Luke Bisby played dozens of video clips and images as he explained how a kitchen fire crept through a fourth-floor window and tore up and across four faces of the building.
One woman was led from the main hearing room at Holborn Bars on Tuesday in apparent distress as the hellish scenes were shown on screen.
Earlier, the fire expert – commissioned to analyse the blaze for Sir Martin Moore-Bick’s investigation – outlined how combustible material was installed on the block’s external facade during a refurbishment.
This included cladding panels with a “highly flammable” polyethylene core, fitted in a way that “directly exposed” this weak point to a cavity separating it from the insulation strips.
The insulation around the window of the flat where the blaze began in turn lacked a protective layer that would have stopped the material promoting rapid flame spread, the inquiry heard.
In addition, voids ran vertically up the tower at certain points from the fourth floor all the way to the crown.
The advance of the fire on June 14 seemed to correspond with the location of these voids, Professor Bisby said.
Playing footage shot between 1.16am and 1.19am – around 22 to 25 minutes after the first 999 call – the expert said the flames had spread up to floors six and seven, focused between the column lines and the horizontal spandrels.
“You will recall that a continuous vertical void exists in the cladding system at this location,” he said.
Once it took hold of the building’s external facade, the “rate of fire spread increased exponentially”, the professor added.
A grim sequence of video clips was then shown, tracing the fire across several hours as it reached the building’s top floor and then spread on to the surrounding sides.
At 1.22am, roughly two minutes after the firefighters had extinguished the kitchen blaze in Flat 16, a jet of water could be seen shooting up the side of the building.
The professor said: “The angle of attack of this jet suggests this is a firefighting jet being operated by firefighters that are within Flat 16, leaning out of the window and spraying upwards in an unsuccessful attempt to extinguish the rapidly spreading cladding fire.”
The crown of Grenfell Tower was blamed for allowing the inferno to spread across the remaining three faces of the block.
Professor Bisby said the crown was “formed largely from vertical channels of highly combustible Reynobond PE ACM panels”.
He told the inquiry that the fire had first jumped from the east face to the south and north face, eventually reaching the west side shortly before 3am.
But, unusually for similar cladding fires internationally, the Grenfell blaze also spread downwards, he said.
“It will be observed that considerable melting and dripping of burning material occurred, primarily along the column lines,” the professor told the hearing.
“It is my opinion that this burning and dripping material is predominantly polyethylene from the ACM rainscreen cassettes.
“We will also see that falling flaming debris landed on horizontal ledges on the spandrel sections and in some cases resulted in localised burning at these locations.”
Firefighter action on the night of the blaze might have mitigated the unexpected downward spread of the blaze, it was claimed.
Professor Bisby said: “It’s noteworthy that both video and photo evidence appear to suggest that the downward vertical fire spread was halted as a result of fire service intervention during the fire.
“This was because water was applied directly to the external cladding, which was able to halt the downward progress of the fire.”
He was the last of three expert witnesses to give evidence to the inquiry.
It is expected that deputy assistant commissioner Andrew Bell, of the London Fire Brigade, will give evidence on Thursday afternoon.