The young lawyer was reading her newspaper, trying not to look nervous. Less than 24 hours after suicide bombers tried to wreak havoc on London for the second time in a month, the 29-year-old did not want to stare at her fellow passengers after boarding the Tube at Stockwell.
"With what had happened the day before, I was determined to act positively," the young woman said last week. "I was trying not to stare at other people, wondering if they were a terrorist."
Her testimony about what happened next could prove crucial to the investigation into the fatal shooting four months ago of Jean Charles de Menezes, a 24-year-old Brazilian electrician mistakenly identified by undercover policemen as a would-be suicide bomber.
The witness, who spoke exclusively to The Independent on Sunday last week, has given a detailed statement to the independent inquiry looking into the shooting of Mr de Menezes, whose death on 22 July prompted a diplomatic row between Britain and Brazil and led to calls for the resignation of Sir Ian Blair, the chief of the Metropolitan police.
Her eyewitness account, coupled with briefings to the IoS from senior police officers and sources close to the inquiry, has cast new light on the catastrophic chain of events that led to an innocent man being shot eight times, in front of terrified commuters.
The findings contradict key evidence disseminated by police sources in the immediate aftermath of the shooting - and paint a picture of confusion, human error and faulty intelligence in the first definitive account of the day Mr de Menezes died.
The lawyer's new testimony to the Independent Police Complaints Commission (IPCC), whose evidence may take more than a year to study, also describes thepandemonium on the Tube train leaving Stockwell as an undercover team of officers mistakenly tailed Mr de Menezes.
Only eight seats away from the Brazilian electrician, she was waiting for the train to leave Stockwell station when she heard a noise. "There was a scuffle to my left," she said. "People by the doors started to get off - that's when I started hearing shots. People were screaming.
"I sprinted down the platform and almost ran into a guy with a gun. I turned and ran towards the other exit. I thought I was going to get shot."
Crucially, no witness statements were taken from passengers who witnessed a firearms officer wrapping his arms around Mr de Menezes, pinning his arms to his side, and another officer pumping eight bullets into his head and shoulder.
The IoS can also reveal:
* Officers watching Mr de Menezes at his flat in Scotia Road, south London, did not activate video cameras to check whether he matched CCTV footage of the 21 July suspects.
* Claims that Mr de Menezes vaulted over a ticket barrier arose because witnesses confused the suspect with plainclothes police in pursuit.
* Cressida Dick, the commander in charge of the Met's Trident firearms unit, was responsible for giving orders to shoot to kill.
* Police marksmen can no longer decide when to fire under Operation Kratos guidelines, which advise officers to shoot suspects in the head without warning.
Sir Ian Blair, who is now the subject of a second IPCC inquiry, could still be held to account if prosecutors can establish that the policy that he implemented directly caused the death of an innocent man.
Investigators have established that police did not issue warnings to Mr de Menezes, who was unaware that he was being followed from his home in Tulse Hill, south London, until he was confronted by officers.
Surveillance officers with stills of the suspects connected with the failed 21 July bombings were watching a block of nine flats in Scotia Road after a gym membership card bearing the same address was found among the unexploded bombs from the day before.
At 9.30am, the victim left the building. Police followed him on to the number 2 bus. As he got off the bus and walked towards Stockwell station, he rang a friend to say he might be late for work because of delays on the Underground.
Eyewitnesses confirm that once inside the station, the electrician, wearing a light denim jacket and not a bulky coat as first reported, touched in with his Oyster card at the barriers and took the escalator down. This is supported by CCTV film from station foyer cameras. He boarded the train at around 10am and took a seat. Seconds later Mr de Menezes was dead.
The run-up to what some eye witnesses called the "execution" should have been recorded by CCTV on the platform, but the camera cable had been faulty for at least 10 days.
The new witness said: "The stories that came out afterwards were terrible. It just didn't ring true - the police should have corrected them. For all the evidence they had on that poor guy it could have been me that they had shot.
"Why the hell did they let him get on a bus if they thought he was going to blow something up? I don't blame the individual officers, but the system as a whole clearly didn't work."
'IoS' investigation: Tube death analysis shows discrepancy between police account and what really happened
1. THE STORY
CLAIM Police initially said Jean Charles de Menezes had come out of a house linked to failed 21 July attacks
FACT The building in Tulse Hill was a three-storey block of nine flats. All residents used the same communal entrance
2. MISTAKEN IDENTITY
Surveillance officers had CCTV stills of the 21 July suspects, including Hussain Osman (right), who slightly resembled the victim. But no positive link was ever made because police failed to send images of Mr de Menezes (left) back to Scotland Yard
3. THE FATEFUL JOURNEY
CLAIM Officers said Mr de Menezes behaved suspiciously by getting on and off the same bus and also wore a bulky coat
FACT He did get off the bus but displayed no other "suspicious" behaviour. He was wearing a light denim jacket
4. THE COMMANDER
The IPCC has established, after initial confusion, that the officer in charge of operations on 22 July was Commander Cressida Dick, and that she was responsible for co-ordinating the surveillance team and gave the order for firearms officers to go to Stockwell station
5. THE TUBE STATION
CLAIM Sir Ian Blair said Mr de Menezes defied a police challenge. Some witnesses said that he vaulted Tube barriers
FACT The Brazilian used his Oyster card at the barriers after picking up a free paper, unaware he was being followed
6. THE CARRIAGE
CLAIM Witnesses said Mr de Menezes fled armed police on to the train platform and then on to a Northern line train
FACT He did run part of the way to catch the train. But once in the carriage he walked calmly to his seat
7. THE SHOOTING
CLAIM Mr de Menezes got to the floor when police pursued him on to the carriage and was then surrounded and shot
FACT A surveillance officer sat near Mr de Menezes, who leapt up when grabbed. He wasshot eight times
8. THE AFTERMATH
CLAIM Police believed he was a suicide bomber, maybe with explosives. Some witnesses saw 'wires' inhis jacket
FACT Investigators found the victim was carrying no weapons, and merely had a wallet in his pockets