Steven Gallant, 42, was out on licence attending a prisoner rehabilitation event when Khan stabbed Cambridge University graduates Jack Merritt, 25, and Saskia Jones, 23, to death on November 29, 2019.
He tackled Khan with a chair and narwhal tusk before helping wrestle him to the ground allowing armed police to shoot him dead outside Fishmongers’ Hall .
Speaking after the incident Boris Johnson praised Gallant and said he was "lost in admiration for the bravery”.
Gallant is serving a minimum of 17 years and is still behind bars for killing firefighter Barrie Jackson in Hull 15 years ago.
However, his prison governor applied for his hearing to be brought forward and it will now be held in April next year, The Times reported.
Speaking about the attack in January, the Prime Minister said: “I’m lost in admiration for the bravery of Steven Gallant and indeed the others who went to the assistance of members of the public on that day and fought a very determined terrorist.
"It is not for the government to decide these things, but it is my hope that that gallantry will in due course be recognised in the proper way.”
His remarks came after Labour’s Karl Turner asked Mr Johnson to pay tribute to his Hull East constituent for taking on the terrorist as he embarked on a killing spree armed with two knives and wearing a fake suicide vest during the Learning Together rehabilitation project event.
At the time of the incident, Gallant said he saw injured people and knew he had to do something.
“I could tell something was wrong and had to help," he said.
"I saw injured people. 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."
Gallant and James Gilligan were jailed in 2005 for carrying out a revenge attack on 33-year-old Mr Jackson.
The pair lay in wait for Mr Jackson outside a pub after believing he attacked Gallant’s girlfriend.
He is thought to have been bludgeoned with a hammer, kicked and punched to death, according to a 2008 Court of Appeal judgment which dismissed Gallant’s application to quash the conviction.
But since going to prison, Gallant has “vowed never to turn to violence again”.
Instead he learnt to read and write and is now in his third year of a business studies degree.