The London Bridge hero who blasted a terrorist with a fire extinguisher was a killer on parole who was friends with victim Jack Merritt.
John Crilly, 48, bravely and selflessly chased Usman Khan after the knifeman fatally stabbed Mr Merritt, 25, and Saskia Jones, 23, during a prisoner rehabilitation event at Fishmongers' Hall last Friday.
Crilly had turned his life around after he was originally convicted of murdering 71-year-old African tribal leader Augustine Maduemezia in February 2005.
The former heroin addict spent 13 years in prison until his conviction was quashed following a Supreme Court ruling on joint enterprise law and he was released in 2018 after admitting manslaughter.
The court ruled the law on joint enterprise, where defendants were prosecuted for murder even if they did not strike the fatal blow, had been misinterpreted.
Crilly was originally jailed by Lord Brian Leveson, one of the appeal court judges who had previously quashed convicted terrorist Khan's indeterminate sentence.
Dramatic video showed Crilly spraying Khan, 28, in the face with the fire extinguisher as kitchen porter Lukasz Koczocik, 38, jabs the terrorist with a 5-ft long narwhal tusk taken from a wall inside Fishmongers' Hall.
About half a dozen heroes chased, tackled and pinned down Khan - who was armed with two kitchen knives and wearing a fake suicide vest - until armed police arrived moments later and shot him dead.
Crilly met and was mentored by Mr Merritt while in prison, where the Cambridge graduate was a course coordinator for the Learning Together programme which helps to rehabilitate inmates.
The pair became friends and Mr Merritt attended Crilly's graduation in September this year after he studied for an Open University law degree.
In the aftermath of the attack, Crilly paid tribute to his friend, writing on Facebook : "RIP Jack. Love you! Missing you so much already! xx."
He wrote in another post: "Why!? This guy, Jack Merrit, the best guy I ever met."
Referring to Khan, who was also being helped by the Learning Together programme, Crilly added: "Jack actually tried helping this guy! To educate him. As he educated me. Jack came all l the way from Cambridge to be at my graduation in m/cr.
"How proud am I to be called Jack Merrit's friend."
Crilly's friends hailed his heroic actions .
One wrote on Facebook: “I honestly think your friend would be proud of you John Crilly for your actions, so many people could have died if it wasn’t for your quick thinking!! Be proud of yourself.”
“You’re a brave man John massive hugs to you!!
“Would have you by my side any day you deserve a medal.”
Another friend wrote: “You’ve been through such a trauma, your response was heroic.
“I’m sure your friend would be proud of you. We all are! Such a s*** world Crilly but you lot took it on n didn’t let him win.”
In December 2005, Crilly, then 34, was sentenced to life with a minimum of 20 years for the robbery and murder of Mr Maduemezia at his flat in Manchester.
The victim died after being punched in the face by David John Flynn, then 38, who was ordered to serve a minimum of 25 years.
As Mr Maduemezia lay dying with severe head injuries, Crilly and Flynn ransacked his flat and made off with a blender and mobile phone.
Speaking when he was released from prison in 2018, Crilly told the BBC: "I had a bad life, I've changed it, I wasn't guilty of murder.
"I totally accept what I did and it was wrong... I would have done the time, I would have done every day of that."
Mr Merritt, from Cottenham, Cambridgeshire, worked on the Learning Together programme associated with Cambridge University's Institute of Criminology which is aimed at bringing offenders and people in higher education to "study alongside each other".
Miss Jones was a programme volunteer from Stratford-upon-Avon in Warwickshire.
Khan was being helped by the programme after he was automatically released from prison on licence in December 2018.
He was halfway through a 16-year prison sentence for terror offences.
Khan, who was living in Stafford, was initially given an indeterminate sentence with a minimum of eight years.
But in April 2013, Court of Appeal judges, including Lord Leveson, quashed the sentence and replaced it with a determinate term of 16 years.