At 1.55pm on Friday, Usman Khan descended the grand staircase leading to the ornate banqueting suite in the basement of Fishmongers’ Hall near London Bridge.
There, academics and former prisoners had gathered for a conference on rehabilitation.
Khan, a convict released on licence and wearing an electronic tag, had been taking part in the conference.
No one gave him a second look when he slipped away. Minutes later he was back – this time with knives taped to his hands and wearing a fake suicide belt – and moving purposefully across the room.
In the words of one academic there, Khan ‘suddenly just flipped’.
A killer at bay: Rampaging knifeman Usman Khan, left, is halted on London Bridge by a Polish chef named Lukasz, centre, armed with a narwhal tusk, and an unidentified man wielding a fire extinguisher
That, at least, is how it appeared. In reality, what came next – a murderous rampage lasting just eight minutes that would leave three dead, including Khan himself – seems to have been well planned.
Khan, 28, had been jailed in 2012 for his part in an Al Qaeda-inspired terror group’s plot to bomb the London Stock Exchange.
He had been invited to the conference, Learning Together, run by Cambridge University’s Institute of Criminology, as a rehabilitated prisoner who had turned his back on his fanatical past.
But as the 150 or so delegates would discover, nothing could be further from the truth.
Making a break: Khan, above centre, tries to escape the have-a-go heroes but more brave passers-by join in
One of the conference organisers, Jack Merritt, 25, was the first to fall victim to Khan’s onslaught.
An unnamed woman, believed to be just inside the entrance to the hall, was fatally injured as the fanatic slashed his way out of the building.
Amid chaos and panic, a witness recalled seeing ‘two, three people stabbed’ with ‘one minor injury and the other two were proper bleeding’.
Anyone crossing his path was likely to receive the same merciless treatment. But Khan had reckoned without the bravery of some of those at the conference.
One, a Polish chef named Lukasz, is believed to have grabbed a 5ft narwhal whale tusk that hung over a doorway in the hall, home of the Worshipful Company of Fishmongers, and began running after Khan as he fled towards London Bridge.
The killer cornered: Police and the London Bridge heroes pin down the attacker
Another man picked up a fire extinguisher and joined the chase.
According to a source, all those involved in tackling Khan – with the exception of Mr Lukasz – were ex-offenders, either on day release or on licence.
One of them was James Ford, convicted of killing Amanda Champion, 21, who had a mental age of a 15-year-old, in Ashford, Kent, in 2014.
His victim’s aunt, Angela Cox, said last night: ‘He murdered a disabled girl. He is not a hero, absolutely not.’
The first call to police came at 1.58pm, by which time the incredible bravery of the now five or six men tackling Khan had become apparent to astonished motorists and terrified passengers watching from the top deck of a London bus.
Around London Bridge, packed with lunching office workers, word of the outrage was beginning to spread.
By now, Khan was on the bridge itself. Ben Middleton, 39, who works for a law firm in chambers at Fishmongers’ Hall, said: ‘I heard a lot of shouting… they were saying, ‘There’s a guy with a machete, get back.’
Gary Lawrence, 48, a volunteer with London Air Ambulance, was stuck in traffic and saw Khan leave the hall with several men in close pursuit.
He watched astonished as the civilian posse chased Khan on to the bridge. ‘One had a stick,’ he said.
‘Another had a fire extinguisher. He was brandishing it at first, then spraying it. The guy with the stick was poking him [Khan]. They approached the knifeman and he stood swiping his knives, one in each hand, around him.’
Gunned down: Khan lies on the ground after being shot by police
One of Mr Lukasz’s colleagues said the chef had run towards Khan as he threatened to set off the fake explosive vest strapped to his body.
He said Mr Lukasz was ‘cut in the hand’, but ‘being stabbed didn’t stop him giving him a beating’. Cecilia Sodero, who watched events unfold from a bus, said: ‘At some point someone said, ‘Oh, he has a knife.’
And we were like, ‘Oh my gosh, this guy is supposed to have stabbed someone.’ People were running away.’
She said the man partially pulled off his black jacket, revealing a ‘very scary device, like a bomb’.
By 2.02pm, the civilians chasing Khan had managed to pin him down. Thomas Gray and Stevie Hurst, two Mini drivers for a London tour based on the film The Italian Job, also joined the fray.
Mr Gray said he ran to the scene and stamped on Khan’s wrist to release a knife. ‘I did what any Londoner would do and tried to put a stop to it,’ he said.
‘He had two knives on him, one in each hand, and it looked like they were taped to his hand. I stamped on his left wrist while someone else smacked his hand on the ground and kicked one of the knives away.’
A suited plain-clothes detective from the British Transport Police also joined the fight and was able to retrieve one of the knives, delicately holding it to avoid smudging possible fingerprints left by the killer.
Kirsten Jones was on a bus when she saw what initially looked like a street brawl. ‘There was a fight going on… and then you realise it was police wrestling with one tall, bearded man,’ she said.
‘He then pulled his coat back, which showed he had some sort of vest underneath. The police then really quickly moved away. He was sort of lying there pulling his coat backwards. The police were shouting at him and staying back from him.’
Those police were armed officers from the City of London Police, who were on the scene by 2.02pm. They ordered the hero civilians to get back. As the last one was pulled away, one of the officers was heard shouting at Khan to ‘stop moving’ as they feared the ‘suicide belt’ was about to be detonated.
At 2.03pm, two shots rang out. Khan’s horrific rampage had abruptly ended.