Britain's 'most dangerous serial killer' will die in prison in an underground glass box following horrific crimes

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

Robert Maudsley has long been regarded as Britain's 'most dangerous serial killer' ever since he was imprisoned at the age of 21.

The now 70-year-old murderer is currently serving a life in prison at Category A HMP Wakefield, widely known as ‘Monster Mansion’ due to the large number of high-profile and high-risk offenders held there.

As a twenty-something year-old sex worker who'd travelled from his hometown of Liverpool to London to make ends meet back in 1974, Maudsley committed his first crime.

He was picked up by a man named John Farrell, 30, 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.

Channel 5

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, 26.

Maudsley was convicted of manslaughter - sentenced to life imprisonment with the recommendation he never gets parole or conditional release - and was sent to Wakefield Prison.

Maudsley later killed two other inmates at Wakefield - Salney Darwood, 46, who was imprisoned for killing his own wife and William Roberts, 56 - although he said he set out to kill seven.

According to his nephew, Gavin Maudsley, 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.

Getty/ David Goddard

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.

In fact, he'll remain in this sealed glass box in the basement of the prison until he dies.

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.

Channel 5

"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."