**Content warning: Mention of child abuse, sexual abuse, rape and details of violence and murder.**

The man considered to be Britain's most dangerous killer will die in a sealed glass box in the basement of a prison.

Robert Maudsley has been in a psychiatric facility and then prison since the age of 21.

The now 70-year-old was placed into solitary confinement in a sealed glass box in the basement of Wakefield prison, England, as a result of his killing three people while in prison and threatening to attack more.

Maudsley - incorrectly nicknamed by the press as 'Hannibal the Cannibal' despite it being found he hadn't actually eaten part of one of his victim's brains - is the longest-serving British prisoner in solitary confinement, where he will remain until he dies.

Channel 5

Maudsley's first crime took place in 1974 while he was working as a sex worker in London.

He was picked up by a man named John Farrell and after Farrell allegedly showed him photographs of children he'd sexually abused, Maudsley garrotted him.

As a teenager, Maudsley received psychiatric help and told doctors he heard voices telling him to kill his parents - his dad having been removed from the family home by social services as a result of physically abusing Maudsley and his siblings. Maudsley later claimed he'd been raped by his father too.

Getty/ David Goddard

Maudsley was sent to psychiatric facility Broadmoor Hospital after garrotting Farrell as a result of being found unfit to stand trial.

In 1977, he and another patient tortured a third patient - convicted child molester, David Francis.

Maudsley was convicted of manslaughter and sent to Wakefield Prison.

Despite briefly returning to Broadmoor, Maudsley later received a whole life order - sentenced to life imprisonment with the recommendation he never gets parole or conditional release - and was sent back to Wakefield.

Channel 5

Maudsley later killed two other inmates at Wakefield - one who was imprisoned for killing their wife - although he said he set out to kill seven.

According to his nephew, Gavin Mawdsley, Maudsley stated he only killed sex offenders, paedophiles or rapists and was planning to kill as many as he could, as revealed in Channel 5 documentary HMP Wakefield: Evil Behind Bars.

Britain's 'most dangerous killer' was subsequently placed into solitary confinement in 1978 and later built a two-cell unit in the basement of the prison where he's remained since 1983.

Orion Pictures

The cell reportedly measures 18ft by 15ft, featuring bulletproof windows, a toilet and sink bolted to the floor and a table and chair made from compressed cardboard.

Maudsley remains in it for 23 out of 24 hours every day.

In a letter, the 70-year-old wrote: "The prison authorities see me as a problem, and their solution has been to put me into solitary confinement and throw away the key, to bury me alive in a concrete coffin.

"It does not matter to them whether I am mad or bad. They do not know the answer and they do not care just so long as I am kept out of sight and out of mind.

"I am left to stagnate, vegetate and to regress; left to confront my solitary head-on with people who have eyes but don't see and who have ears but don't hear, who have mouths but don't speak. My life in solitary is one long period of unbroken depression."