A previously unidentified prisoner who helped tackle Usman Khan, the London Bridge knife attacker, has spoken for the first time about his role in the fatal confrontation.

Steve Gallant, who attempted to subdue the terrorist with a narwhal tusk, was spending his first day out on licence at a criminal justice conference on 29 November last year when Khan began stabbing volunteers attending the event.

Gallant, 43, serving a life sentence for murder, has issued a statement through his lawyers, Hudgell Solicitors, revealing his identity.

The gathering at Fishmongers’ Hall in the City of London, was a workshop for a prison-based education project, Learning Together. Gallant said: “When I heard the noise from downstairs, I went to investigate. There were orders to stay in the conference hall, but I could tell something was wrong and had to help.

“On my way downstairs I saw injured people. It was obvious who was responsible. Khan was stood in the foyer with two large knives in his hands. He was a clear danger to all, so I didn’t hesitate, I used a narwhal tusk and then a chair to hold him back and prevent him from hurting others.

Steve Gallant, centre, wearing a purple jumper, crouches over the terrorist Usman Khan on London Bridge. Photograph: web

“Khan also showed us the bomb around his waist in an attempt to frighten us. We then chased him on to London Bridge and restrained him until the police arrived.”

Gallant was pictured on London Bridge along with Darryn Frost, a civil servant, and John Crilly, a former prisoner, as they cornered and fought to disarm Khan.

Frost had grabbed one of two narwhal tusks from the wall on Fishmongers’ Hall and handed it to Gallant who used it to defend himself against Khan. The tusk snapped and Gallant seized a chair which he hurled at Khan.

Frost then took a second narwhal tusk and along with Gallant and Crilly pursued Khan out on to the bridge where they subdued the terrorist until police arrived.

Gallant was sitting on Khan to prevent him escaping when officers ordered him to stand back. He was shot dead; it later emerged the suicide vest was false but intended to intimidate victims.

In his statement, Gallant thanked “everyone who did their best on that tragic day”, including “Lukasz, a Polish chef who joined in, and John [who] were extremely brave. Had [Darryn] not passed me the narwhal tusk at that crucial moment, not only could I have been killed, the situation could have been even worse.”

Gallant paid tribute to Jack Merritt, whom he knew, and Saskia Jones, the two Cambridge University students who died.

Gallant said: “I first met Jack in 2016 when he became a course coordinator. Jack didn’t care who you were, he cared about you and your future, he saw who you could become and did not define you by your past. He was a role model and a friend.

From left: Darryn Frost with narwhal tusk, Steve Gallant (behind the attacker Usman Khan) and John Crilly on London Bridge. Photograph: web

“Losing Jack and Saskia has been an unbearable blow … but I am certain they would wish us to continue developing Learning Together and enriching the lives of everyone associated.”

Gallant was convicted of the murder of Barrie Jackson in Hull in 2005 and was sentenced to life imprisonment with a minimum term of 17 years. He is not eligible for parole until 2022.

He entered prison with limited reading abilities but has since written a play which has been read in rehearsal at the Royal Court theatre in London.

Gallant said: “Once I’d accepted my punishment, I decided to seek help and vowed never to turn to violence again. When you go to prison, you lose control of your life … However, bettering yourself becomes one of the few things you can do while reducing the existing burden on society.”

Addressing his victim’s family, he said he offered “sincere apologies” for the hurt caused. “I can never bring that life back, and it is right that I was handed a severe penalty for my actions.”

Neil Hudgell, Gallant’s solicitor, said: “I find him a very impressive and articulate individual. He is making great strides towards full rehabilitation.”