A firefighter burst into tears at the Grenfell Tower Inquiry as he was asked to recall the first time he realised the block was engulfed by flames.
Christopher Secrett, a crew manager from North Kensington red watch, was forced to halt his evidence during a second day at Holborn Bars.
He was part of the first response to the fire on June 14 last year and had been running the bridgehead two floors below the initial kitchen fire.
This was a safe-air space for the firefighters and also the point of contact for incident commander Michael Dowden, who was outside.
His colleagues reported that the fourth-floor fire was extinguished, but it had actually spread to the flammable cladding outside and shot up the external facade.
Mr Secrett became overwhelmed by emotion as he remembered looking up at the tower when he went out to liaise with Mr Dowden.
It was the first time he had seen the extent of the inferno's spread, barely half an hour after they had first been called at 12.54am.
"You look up the tower and you say the fire must have been at least three-quarters of the way up the building?" lead counsel to the inquiry Richard Millett QC said.
Mr Secrett began breathing heavily and tried to maintain composure, insisting he was fine when offered a break.
Mr Millett asked for Mr Secrett's statement to be removed from the screen, while the firefighter sipped his water.
He was then read a section of the statement in which he asked Mr Dowden: "Jesus Christ, what have you made it?", referring to the number of fire engines requested.
"I said I would make it 15-20 because it looks like we are losing it. By this I meant that the fire appeared to be getting away from us; it was doing what it wanted rather than us controlling it."
Mr Secrett then started crying uncontrollably, pinching his eyes tightly as he sobbed.
Inquiry chairman Sir Martin Moore-Bick said: "I think we need a break, whether you think so or not, we need a break."
His emotional fragility again underscored the tremendous toll that the tragedy has taken on those who tried to stop it.
Several firefighters, including senior officers, have broken down during their evidence, prompting the inquiry to offer them breaks at least once an hour.
Sir Martin told Mr Millett when the hearing resumed on Thursday that the crew manager should be allowed a break in half an hour.
In his written statement, Mr Secrett had described hearing Mr Dowden becoming "a bit flustered" over the radio and ordering more fire engines, despite crew manager Charles Batterbee assuring him the internal blaze was out.
He wrote: "I told him to slow down because the fire was out. I realised something was amiss ... by now there was lots of radio traffic.
"It transpired although the fire had been extinguished inside the flat, the fire was travelling on the outside of the building. This is something that can happen and I have seen before. Fire can spread to the flat above via the window."
Recalling what he eventually saw, Mr Secrett said: "The whole side of the building was on fire and there was no way we are going to put that out quickly.
"It was now a significant fire which I would describe as raging and very fierce.
"The heat radiating was really intense. I could see a lot of sparking and fizzing of fires spreading everywhere. It was a big wall of fire and so intense.
"Whatever was fuelling it was doing a good job."