When Usman Khan emerged into the hallway armed and ready to begin his rampage of terror it was his mentor Jack Merritt who was the first to rush to stop him.
Friends and colleagues have said that he had found an "affinity" with the convicted terrorists, and was convinced that he could “guide him to redemption”.
But that faith was repaid with violence as Khan slashed out at those who tried to prevent his murderous spree.
A detailed account of the first moments of Friday’s London Bridge attack has emerged for the first time along with stories of the incredible acts of heroism of members of the public.
Khan had been given special permission by the authorities to travel to the capital unsupervised and had in the morning given a “convincing” talk about his rehabilitation during a workshop at Learning Together’s fifth anniversary event.
But the convicted terrorist, who had only been released from prison 11 months earlier, used a break in the afternoon’s proceedings to go into the toilets and tape a fake suicide vest to his body and knives to his hands.
At around 1.55pm he emerged into the hallway on the first floor of the Fishmongers Hall and began his attack.
Mr Merritt, 25, who had helped to organise the event, ran out to try and calm him down along with others who had been in the Banqueting Hall of the Grade I listed building, sources told the Telegraph.
Bryonn Bain, an associate professor with the University of California in Los Angeles who spoke at the conference, said that the “brave” Cambridge graduate “was the first line of defence, he was the first person to confront him”.
Lukasz Koczocik, a worker at the venue had been cleaning glasses in the basement and heard the screams, also ran to help.
“He goes towards the trouble, he gets there on the first floor and it is very clear that there’s a bad guy, he’s got two knives in his hand, there’s screaming, there’s chaos,” Toby Williamson, chief executive of the Fishmongers Company, told the BBC as he paid tribute to his staff.
Mr Koczocik armed himself with a long stick and “charges towards the bad guy” but hits “something protective”.
"But he’s buying time and he allows others to escape to move to adjacent rooms and at that point he has about a one minute one on one straight combat,” Mr Williamson said.
“This guy Khan then works his way up Lukasz pole slashing with his knife, he takes five wounds to his left side.”
Mr Bain said that it “felt like a warzone... it felt like total chaos."
Mr Koczocik, who it was announced on Monday will be getting an honour for bravery in his native Poland, started to lose strength but two men from the conference rushed to intervene.
One was armed with a fire extinguisher and the other with a narwhal tusk that he had ripped from the wall.
“They come and join the fight and it is pretty gruesome and I think the terrorist decided he was outnumbered, he runs though and goes down the main staircase and the next bit of hell is he is at reception and he can't get out the front door," Mr Williamson said.
Gareth, the doorman "is pushing the door shut as good as he can" whilst another worker named only as Dawn calls the police.
People were trying to keep the door closed and Khan was swinging knives at them, it was said.
Saskia Jones, a 23-year-old who had volunteered with Learning Together, a Cambridge University rehabilitation initiative, was also fatally wounded inside the building and at least two others were seriously injured.
Finding himself trapped Khan turned to the girls in the cloakroom, Alla and Sandra, and gives them a “hell of a time” before a showdown in the entrance hall with Mr Koczocik “leading the charge”.
Mr Williamson said: “Andy the last guy introduced here, our maintenance man, he’s a Ministry of Defence ex-policeman and he’s also a pretty cool customer.
“But when the knife goes to his chest and kill or open the door is the choice he pauses for a moment, he’s reluctant to spill all this out onto the pavement when members of public are going to be facing the same problems but he makes exactly the right choice, the door’s opened, out the terrorist falls and the first one after him is Lukasz shouting at everyone to get out of the way, to get back.
"But members of the public just don’t do that nowadays, they do what they needed to do, they join in and the man with the fire extinguisher, the man with the narwhal tusk, they are all in there.”
Footage has emerged of the two men linked to the charity spraying and prodding Khan with the Narwhal tusk before he is tackled to the floor.
Some of the have-a-go-heroes were former convicts who were attending the event, it was said.
Moments later, at 2.02pm police marksmen arrive and after pulling the final member of the public away from Khan he is shot dead.
But in his wake he left a trail of devastation, with Mr Bain recognising: “I saw people die. I saw things that I will never be able to unsee."
Those who will feel that devastation most keenly are the family and friends of Miss Jones and Mr Merritt, who had dedicated their lives to helping others.
David Merritt wrote that his son was “was selfless in his dedication to make things right in every second of his life”.
“Jack devoted his energy to the purpose of Learning Together: a pioneering programme to bring students from university and prisons together to share their unique perspectives on justice,” he said.
“Unlike many of us, Jack did not just go to work. He lived and breathed fire in his pursuit of a better world for all humanity, particularly those most in need.”
It emerged that Khan had shown “an affinity” towards Jack Merritt, the Learning Together course co-ordinator who helped mentor and supervise him.
One source at Cambridge said: “We’ve heard that Khan was initially very sceptical about the group that wanted to help him rebuild his life but built up a mutual understanding and respect towards Jack. It wasn’t so much a friendship, but there seems to have been a special bond, a closeness.
“Jack was convinced he could guide Khan to redemption, I think he really believed that he could turn his life round. “He even became a case study for the group.
“That’s why it’s so galling that Jack was murdered in cold blood by the man who appeared to have bonded with him. “