A firefighter who carried out a solo journey up Grenfell Tower has described how the widespread smoke made him realise people were going to die.
Justin O'Beirne, a member of North Kensington crew with 20 years' experience, undertook a mission "off his own back" to investigate the floors above the site of a kitchen fire on June 14 2017.
In a written statement, published by the inquiry into the blaze, he described bolting from floor to floor soon after arriving - with his shock growing at the extent of the spread of smoke.
But despite multiple radioed warnings sent directly to incident commander Michael Dowden on the ground floor, the message was not received.
His evidence came as it emerged that a daring rescue had been mounted that night by one of his colleagues, who helped two men from a fifth-floor window using a ladder.
Mr O'Beirne did not take breathing apparatus with him, assuming that he was well-respected enough for his guidance to be heeded by Mr Dowden, the inquiry heard.
He travelled between floors five and nine in "no more than four minutes", he told a hearing at Holborn Bars on Monday, agreeing that that his decision to act as "free operator" was not normal.
Asked why he had acted in such a way by counsel to the inquiry Richard Millett QC, he said: "Inquisitive, maybe... once I saw the fire on the fifth floor, I didn't have any equipment to deal with that and I thought I would investigate further and I found myself investigating a bit more, I guess."
He also agreed when the lawyer suggested he had acted "off his own back", prompting the response: "You're very much a free agent rising up to there and finding out what the conditions are?"
Mr O'Beirne said: "I was trying to gather information."
His statement said he first visited the fifth floor - directly above the flat where the fire originated on the fourth floor - where a family had told him their home was ablaze.
He wrote: "I radioed down to (watch manager) Dowden, using my handheld radio, and said something along the lines of 'the flat above the fire floor is on fire, their kitchen is alight. We need a BA crew and breaking-in gear' ... I didn't get a reply but I believed my message had been transmitted."
Mr Dowden said in evidence he did not receive the crucial information, which indicated compartmentation within the block was compromised and an evacuation could be required.
He was confronted by "thick black smoke" when he looked through the letter box a few minutes later.
The firefighter radioed Mr Dowden again and went up to the sixth floor, where he again found smoke and a fleeing family, before finding smoke on the seventh floor too.
He chose not to knock on the door of the flats he passed, thinking residents would be safe inside, the inquiry was told.
Another message was sent to Mr Dowden, but Mr O'Beirne "assumed he was still very busy but that he could hear me", according to the statement.
On Monday, Mr Millett asked the firefighter: "Did you not think it was strange no-one was speaking to you?"
"No, it wasn't that strange, sorry," he replied.
Smoke was also apparent on the eighth floor, his statement said.
Mr O'Beirne wrote: "It began to dawn on me, as I was going up and it was getting smokier, that people were in danger from smoke inhalation."
He then found no smoke on ninth floor but more smoke on the 10th floor, causing him to pause on the stairwell, where there was "just an eerie silence".
The statement continued: "I realised then that something wasn't quite right there and it wasn't a normal fire. I thought that there would be people
who were going to die because of the amount of smoke in the lobbies of the different floors, presumably due to more flats being alight.
"I thought that we wouldn't be able to get enough fire engines and firefighters up those stairs to get everyone out."
He added: "I feel I have an answer for anything, for any problem, but this didn't seem normal and I didn't know what to do."
The firefighter told the hearing that he believed at the time the smoke had come through "windows" or the lift shaft, not due to compartmentation failing.
In his lengthy description of the night, Mr O'Beirne spoke of "mayhem" in the foyer of Grenfell Tower and recalled seeing an American man wearing a baseball cap trying to enter the building with an axe to save people.
Mr O'Beirne also recounted the grim moment he realised a man on the 16th floor with mobility issues would not survive, after his son had begged for help.
The statement said: "It was so hot they couldn't get to him and it wasn't worth putting themselves at any more risk, as the guy wouldn't be able to survive in those conditions for more than three minutes. I knew that the guy's dad wasn't going to be alive."
His colleague, firefighter Thomas Abell, explained in his written statement how he used a 13.5-metre (44ft) ladder to rescue two men from a window at an early stage of the blaze.
He said: "Understandably this took a bit of time as it was a daunting experience for the male, but slowly he managed to climb on the ladder
and descended to the Mezzanine level."
Firefighters will be giving evidence at Holborn Bars all week.