He will argue that after nearly half-a-century in jail, most of it in solitary confinement, he is safe to be released.

Justice Secretary Dominic Raab is opposing his parole and will argue that Bronson, 70, is a high risk of serious harm to the public.

Bronson sent Sky News a postcard from his prison cell last week.

It showed an everyday London street scene - to him, freedom.

He was confident he would be released and wrote: "They should have compassion for my mother. It's her life-long dream to see me free and happy."

Bronson was jailed for armed robbery in 1974 and, but for a couple of brief episodes of freedom, has been in jail ever since.

His original seven-year sentence has been extended many times because of his violent attacks on prison staff and fellow inmates.

In 1999, he held an art teacher hostage for two days in Hull prison and, although he didn't physically hurt him, his victim was left so traumatised he never went back to work.

Bronson was given a life sentence, with a minimum term of three years, but has had many parole bids turned down because of subsequent violent episodes.

His lawyers will argue that it's eight years since his last conviction and four years since an internal prison adjudication for violence.

Bronson is currently assessed as a medium risk to staff and fellow inmates, but is still a Category A prisoner held in the close supervision centre (CSC) at Woodhill Prison near Milton Keynes.

His solicitor Dean Kingham said Bronson, who now calls himself Charles Salvador, is deliberately being prevented from making progress towards a less restricted regime.

He said: "It is clear to me that Mr Salvador is a political prisoner, given the lack of political will to progress someone as high profile as him. By keeping him in CSC conditions the (justice secretary) is trying to influence the Parole Board."

Bronson's family and supporters say it is unfair to keep him in jail when prisoners convicted of more serious offences have been granted parole.

He has also shown he would be able to work and support himself through his drawings, which sometimes sell for several thousand pounds.

In a voice message to Sky News from his cell last year, Bronson said: "It's an absolute liberty. I've never murdered anyone, I've never raped anyone. What am I in jail for? People don't believe it. They think I'm a serial killer."

Former Metropolitan Police detective chief inspector Simon Harding said: "Bronson has an incredibly violent streak and it's very, very risky to release people like that.

"And then, what happens if he is released? There's all the monitoring involved because he will be on a life licence. He's a very dangerous man who's could be released into society very shortly."

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The Parole Board hearing is expected to last for three days, with a decision announced two weeks later.

The board could recommend freeing Bronson, moving him to an open prison or keeping him locked up.

The justice secretary can block a recommendation to release Bronson, but such a move would ultimately be decided by the courts.

The board will hear from prison and probation staff, a lawyer for the justice secretary and Bronson himself.

The hearing is being held in public at the Royal Courts of Justice, with Bronson appearing by video link from jail.

Consultant psychiatrist Dr Bob Johnson, who first treated Bronson more than 30 years ago, said he should be freed.

"The Parole Board should say 'this man has been locked up for 50 years, he has 50 years of problems, violence and unruly behaviour, but we've decided that he's now low enough risk'," he said.

"I think he probably is, but the transition from 50 years inside to outside life is going to be very, very dramatic."

Read more:
Charles Bronson says he can 'taste freedom'
Bronson claims he got phone ban after sending Sky News audio message

Dr Johnson was a controversial figure at Parkhurst Prison on the Isle of Wight, where he treated dozens of murderers and other violent men such as Bronson.

Instead of prescribing control drugs, he encouraged prisoners to understand and confront the reasons for their behaviour, which was often rooted in childhood trauma.

When the Home Office ended his contract, Bronson wrote him a letter in which he lamented his sudden departure.

He wrote: "A sad day to see you go, but I must admit I admire your principles. It's a rare sight to see a doctor stand up to this system.

"Dr ****** was a man who believed in 'drug control', whereas you believed in humanity, then trust.

"Your way obviously worked as you cut the violence."