The terrible tales of the survivors of the attack on the World Trade Centre and of the split-second decisions that saved their lives became clearer.
As they scrambled down the narrow stairs of the Centre's south tower, many workers were told to return to their desks, despite the flames billowing from the building's twin.
Anthony Gould, a British man working on the 91st floor, explained how he owed his life to his decision to ignore that advice and continue to make his escape.
Minutes later, a second hijacked jet hit the south tower, which collapsed before everyone could be evacuated.
Mr Gould's story was among many extraordinary accounts of workers who managed to flee to safety, emerging from the buildings after almost an hour only to watch them crumble minutes later. Too many more, including at least 100 Britons, were not so lucky.
"Other people on their way out took the advice of fire marshals and officials that our building was safe and that, while we were welcome to vacate if we wanted to, it was fine to go back to our desks as well," Mr Gould said.
"At that stage nobody knew what it was that had caused the explosion in tower one. I guess some people thought that if there was debris coming from the first tower the safest place to be was inside.
"How could anybody have known that the second tower was going to be hit? The reason I vacated was the fear that there was going to be some debris from tower one which was going to fall on tower two."
When the lifts stopped operating after the first plane hit the north tower, the 36-year-old Guildford man, who now lives in New Jersey, chose to make the long journey downwards.
"There wasn't total panic until the plane hit the second tower. It was only then that people realised that this wasn't an accident."
As many as 40 per cent of Mr Gould's colleagues remained unaccounted for.
Stephen Blackburn, vice-president of Credit Suisse First Boston Bank, almost made a similar mistake, telling his Nottingham family he planned to remain in the sanctuary of his office. Within the hour they watched the buildings collapse, believing he was inside.
"We managed to get through to Stephen on the phone in his office. He was still there after both planes had gone into the buildings," his father Alan said.
"He said he was going to stay inside because it was safer there than outside with all the debris falling from the sky. Then we rang off and a short while later we watched the television as the buildings collapsed. You can imagine what went through our minds thinking if he had still been inside."
The West Bridgford family endured a five-hour wait before Mr Blackburn could get through to his wife in New York, who relayed the message to his parents. "He had been evacuated before the buildings came down, but had not been able to let us know because his mobile wasn't working," his father said.
Dermot Finch, 33, was having breakfast in a hotel annexe of the north tower when it was hit by the American Airlines Flight 11 Boeing 767. Mr Finch, who worked as First Secretary (Economic) for the Treasury, was seconded to the US in June to begin a four-year project for the Foreign Office.
"The building shook and outside of my window I could see burning debris fall to the ground. The connecting roof between my room and the tower was alight. I just thought a bomb had gone off. As people were pushing to get out the second plane hit, causing panic," he said from his Washington home.
He was evacuated to the reception area as the next plane crashed into the second tower.
Trapped by descending debris, he was forced to sit tight for half-an-hour before his group was led to safety two by two, running through falling fragments of building.
"There was a strange sort of cinematic half-an-hour when people were just watching it all happen, watching the people fall from the towers.
"But I made a conscious effort just to get out of the area. There were some people taking photographs, others were watching and I was just walking away from it," he said.
Told to make his way towards the river, he was caught in Wall Street as a cloud of rubble from the collapsing tower rolled towards him.
"There was, as you have probably seen on the television, an avalanche of flying debris whizzing down the road.
"The NYPD was standing at the entrance to the New York Stock Exchange yelling at people to get inside so I ran towards them. Ten seconds after I had got inside, the police closed the door and pulled down all the shutters. If I had been standing outside 20 seconds longer I would have been overcome by the debris."
Mr Finch then spent more than two hours inside the Stock Exchange before making the two-hour walk to the British Consulate, where he telephoned his father, Wilf, at the family home in Clitheroe, Lancashire.
Wilf Finch said: "After seeing the television coverage of the aircraft striking the towers I was very much preparing myself for the news that my son was among those who had been killed."
Christopher O'Driscoll, a 43-year-old from Kent, managed to escape to safety a mere 10 minutes before his building crumbled, after a tense 45-minute journey down the stairs.
The banker was on the 81st floor of the north tower when it was hit. Mr O'Driscoll, who has worked for the Bank of America since he was 18, was on a short business trip and had stopped at the company offices on his way home.
He eventually managed to contact his wife Karen, 42, an English teacher in Croydon, to tell her he was safe.
She said: "I just want him to come home and to hug him. He's very lucky to be alive. Initially they thought that it was a light aircraft which had hit the building and there wasn't any panic as they evacuated. It wasn't until they stepped outside that he realised the magnitude of what had happened."
"He certainly had a close shave. It took him a long time to get out of the building as the staircases were very narrow but he did not want to make a fuss about him with such loss and sadness," his mother-in-law, Peggy Crouch, added.
"The horror of it. I think it will stay with people forever. The loss of so many innocent people in such a dreadful way."Reuse content