A single thought ran through David Jeffery's mind - "I've got a seven-week-old baby at home and I don't want to die."
The walking wounded were lead along the tracks to King's Cross
Their carriage fast filling with suffocating smoke, the 36-year-old persuaded his fellow Tube travellers to prise open the doors with an umbrella.
But as clouds of the thick black smoke billowed in, he saw his only chance of survival was to flee the burning train.
He made his way through the panicking passengers to the back of the carriage.
David's day had started badly and it was about to get a whole lot worse.
He had been late for work and delays on the Piccadilly Line had meant he had had to wait five minutes for a train at King's Cross.
"When I finally got on a train, it was completely heaving," David told BBC News.
"Some people were left on the platform who couldn't fit in."
They were the lucky ones.
David boarded the rear carriage of the train, rightly assuming it would be the least busy.
He was still congratulating himself on his foresight when he heard "a really loud thud".
The train shuddered to a sickening stop, the lights failed and, with the passengers plunged into pitch darkness, a "good few seconds of silence" followed.
"I thought the driver would say, 'We've had a bump and will get you to Russell Square as soon as possible'," said David.
David leapt from the driver's cab at the rear of the train
But looking towards the speaker above his head, anticipating the driver's announcement, he realised it was now dangling from the ceiling and thick black smoke was billowing into the carriage from the space it had occupied.
More smoke poured through the air vents above the windows and between the closed doors.
"I could hear people saying prayers," David added.
"And then I could hear people saying the carriage in front of us was on fire - which put the fear of God into me.
"People were starting to panic, and a few started saying, 'Calm down, we will be okay' - but, with the smoke filling the carriage I thought, 'How long can we last in these conditions?'
"I tried not to look people in the eyes because we all knew we were thinking the same thing - and it wasn't very nice."
The train was full when David boarded at King's Cross
Having failed to free his fellow passengers by prising open the carriage doors, David pushed his way to the rear of the train, where, miraculously, he found the door to the driver's cab unlocked.
He grabbed the driver's phone - but the line was dead.
David began blindly pushing buttons, flicking switches and pulling levers in a desperate attempt to sound the alarm.
When nothing worked, he decided to leap onto the tracks and run back to King's Cross for help.
As he prised open the door to the driver's cab, the passengers behind him, fearing for his life, shouted for him to stop.
"Adrenaline was pumping so fast I didn't know what I was doing," he told BBC News.
David ran until he found a police officer at the top of the escalator
"I didn't know if the tracks were still live or whether another train would come round the corner and hit us - but I just thought, 'Stuff it, if I stay here I have no chance'."
Running along the tunnel, David tried to keep clear of the electrified rail - but in the darkness it was impossible for him to see where he was treading.
Finally rounding the bend, he caught his first glimpse of light at the end of the tunnel.
Seconds later David was clambering onto the now deserted platform at King's Cross and running screaming up the escalator.
At the top he found a police officer who "looked at me as if to say, 'Where the Hell have you come from?'
Through a throat clogged with thick black soot, David was able to convey the seriousness of the situation underground - but even after he had been given water and examined by medics he remained unaware he had been the victim of a bombing.
David was determined to live to see girlfriend Rachel and baby Daisy
"People were crying and putting their arms around me and asking if I was okay, but I still didn't realise it was a bomb - you never think it will happen to you."
David himself cried as he watched the wounded being lead up into the station.
"I saw people coming up covered in blood, barely able to walk - one guy's cheek had been blown off, a woman's leg was mangled up."
Then he began his long journey back home to his girlfriend, Rachel, and their new baby, Daisy.