A petition calling for the release of Charles Bronson, the man dubbed the most violent prisoner in Britain, has gained more than 10,000 signatures.
Supporters of Bronson, who has convictions for armed robbery, kidnap and assaulting prison staff, claim that the 61-year-old is now a changed man, having undergone therapy behind bars.
Friend Lorraine Etherington said: "I would love for No 10 and the politicians in positions of power to look over his case, to be big enough to look beyond the name and reputation that precedes Charlie.
"We feel he's served enough time. There are murderers who've got out after serving less time than Charlie. He hasn't killed or raped anyone."
Bronson is one of the UK's longest serving prisoners, having spent much of the last 40 years incarcerated. Next February, his 1999 conviction and life sentence for kidnapping and falsely imprisoning prison art teacher Phil Danielson for two days is to be reviewed by the Criminal Cases Review Commission.
The incident was portrayed in the critically acclaimed 2008 film Bronson, in which Tom Hardy played the title role. Danielson claimed after its release that the incident had triggered a nervous breakdown, and he has been unable to work since.
But Bronson's legal team argues that the case should be sent back to the court of appeal as judge Ronald Moss allowed the case to proceed after Bronson dismissed his legal team, then refused to allow Bronson to enter a plea that he acted under "circumstances of duress" under the belief that he was to be transferred to a secure unit where he had previously been "psychologically tortured".
Etherington said: "The flip side of the film was that it showed Charlie only up to the year he got the life sentence, not the reformed man he is today."
Bronson's prison saga began in 1974 after he was sentenced to seven years for stealing £24 in an armed raid. He was imprisoned again in 1988 and 1992 for robbery and intent to rob.
Following a series of attacks on inmates and prison staff his notoriety grew, and he now spends 23 hours a day in solitary confinement in the "Hannibal cage" at HMP Wakefield.
While jailed, he has written a dozen bestselling books, broken world records for press-ups and sit-ups and sells artwork to raise money for children's charities. Recently, he sent a hand-painted birthday card to a three-year-old girl with leukaemia.
Supporters point to the fact that while previously Bronson was accompanied by five prison wardens whenever he left his cell, the number has recently been reduced to four as evidence that he is a changing man.
"I'd ask people to remember that, upon his previous releases, Charlie had no direction, no guidance and little support," said Etherington, who is secretary of the Charlie Bronson Appeal Fund.
"All he wants to do now is find somewhere private to live, do a little travelling and make some money from his art work, which currently takes up most of his days and through which he's raised a lot of money for charity.
"He has no wish or need to return to crime and is a totally different man to the one he was all those years ago - more mature, calmer and capable of dealing with his frustrations in a more appropriate way."
In a letter to a friend recently, Bronson said he felt he was now at a crossroads. "I'm still a category A prisoner, still in a cage, still isolated. I'll either walk free from this appeal or I'll die a very old man in prison," he wrote.