Steven Gallant, who was awarded a Royal Pardon for his actions, was one of three men who restrained Khan until armed police arrived at the scene in November 2019.

Khan, who had two large knives and a fake suicide belt, stabbed Cambridge graduates Jack Merritt 25, and Saskia Jones, 23, and injured three other people before running on to London Bridge.

Giving evidence at the inquest in April this year into the victims’ deaths, Mr Gallant said he “whacked” Khan with a narwhal tusk but was empty-handed by the time of the battle on the bridge.

Court artist sketch of Steven Gallant during the inquest into the terror attack at Fishmongers’ Hall

A spokesperson for the Parole Board said: “We can confirm that a panel of the Parole Board has directed the release of Steven Gallant following an oral hearing.

“Parole Board decisions are solely focused on what risk a prisoner could represent to the public if released and whether that risk is manageable in the community.

“A panel will carefully examine a huge range of evidence, including details of the original crime, and any evidence of behaviour change, as well as explore the harm done and impact the crime has had on the victims.”

The decision on release is provisional for 21 days subject to any appeal by the Justice Secretary.

Mr Gallant was jailed for life with a minimum term of 17 years in 2005 for the murder of a firefighter in Hull.

He had been on day release at the event for reformed prisoners in Fishmongers’ Hall when he helped end Khan’s rampage.

His actions on the day later saw his sentence cut following an intervention by the Queen.

The Ministry of Justice revealed in October that the monarch had employed the little-used “Royal Prerogative of Mercy” to bring Mr Gallant’s case before the Parole Board 10 months early.

Usman Khan

It was considered at a remote oral hearing on June 21, during which Mr Gallant gave evidence.

In a summary of the Parole Board’s decision, it said the panel had recognised his conduct during the Fishmongers’ Hall incident but “was clear that it was not a reason to direct his release”.

The board said professional witnesses had recommended Mr Gallant be released on licence, telling the panel he had “worked hard to understand and address his risk factors and to bring about a change to his life”.

Of its decision, the board said: “After considering the circumstances of his index offending, his pattern of previous offending, the progress made while in custody, the details of the release plan and all the evidence presented at the hearing, the panel was satisfied that Mr Gallant was suitable for release.”

Conditions of his release on licence would include a curfew, staying at a designated address and to comply with an exclusion zone to avoid contact with his victim’s family.

During the inquest for Mr Merritt and Ms Jones, Mr Gallant recalled a crowd of bystanders gathering and somebody suggesting to “give him (Khan) a kicking”.

He told jurors: “I said no, we had control of him at that time. It would make it more difficult.”

Mr Gallant said Khan managed to get up, so he gave the suspect “a couple of uppercuts to the face”, which he said helped to “stun him a little bit”.