The cladding system on the outside of Grenfell Tower was so conducive to the spread of fire it did not support the "stay put" policy normally in place for a building of its type, a report has found.
The "stay put" strategy pursued by the fire service on June 14 last year had "effectively failed" barely half an hour after the fire started, at 1.26am, Dr Barbara Lane wrote.
She also claimed that the key players involved in the 2016 refurbishment had not ascertained how the new cladding system would behave in a fire.
Fire safety engineer Dr Lane made the remarks in an expert report commissioned by the Grenfell Tower inquiry on the fire protection measures within the 25-storey building.
Tests showed the materials forming the cladding system, individually and together, did not comply "with the recommended fire performance" set out in guidance for a building of that height, the report said.
She wrote: "Additionally, I conclude that the entire system could not adequately resist the spread of fire over the walls having regard to height, use and position of the building.
"Specifically, 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.
"There were multiple catastrophic fire-spread routes created by the construction form and construction detailing."
The windows lacked fire resisting cavity barriers and were surrounded by combustible material, meaning there was a "disproportionately high probability" of fire spreading to the cladding, she added.
The report also claimed key players involved in the 2016 refurbishment were not aware of how the new cladding system would behave in a fire.
Dr Lane wrote: "I have found no evidence yet that any member of the design team or the construction ascertained the fire performance of the rainscreen cladding system materials, nor understood how the assembly performed in fire.
"I have found no evidence that Building Control were either informed or understood how the assembly would perform in a fire."
Neither the Tenant Management Organisation nor London Fire Brigade recorded how the cladding would respond to a fire in their risk assessments, she said.
Seventy-one people were killed during the tragedy in Kensington on June 14 last year.
Another died in January after a long battle with a pre-existing condition, having never left hospital since the fire.
Four further expert reports have been released as the first day of evidence gets under way before Sir Martin Moore-Bick in Holborn Bars, central London.
In his opening remarks, Richard Millett QC, counsel to the inquiry, said: "The fundamental question which lies at the heart of our work is how, in London in 2017, a domestic fire developed so quickly and so catastrophically that an entire high rise block was engulfed, and how it was that 71 people lost their lives in a matter of hours, leaving family and friends in shock, grief and bewilderment."
Mr Millett said the Grenfell probe was the "largest public inquiry ever established" in terms of numbers of participants.
There are 533 individual core participants, of which 21 are children who have not been named.
Some 29 organisations are core participants, including 19 commercial bodies, eight public bodies and two trade unions.
He said the inquiry must proceed quickly "in light of the obvious risk to public safety posed by exterior fires on residential tower blocks".