He was one of 12 children, born in the Toxteth area of Liverpool, and spent most of his early years in Nazareth House (an orphanage run by nuns) in Crosby, Liverpool. At the age of eight, he was retrieved by his parents and beaten regularly until he was eventually removed from their care by social services. During the late 1960s, as a teenager, Maudsley was a rent boy in London to support his drug addiction. He was finally forced to seek psychiatric help after several suicide attempts. It was during his talk with doctors that he claimed to hear voices telling him to kill his parents. Maudsley claimed that he was raped as a child, and such early abuse may have left deep psychological scars. He is quoted as saying, 'If I had killed my parents in 1970, none of these people need have died.'
In 1974, Maudsley garrotted a man who picked him up for sex after the man showed Maudsley pictures of children he had sexually abused. Maudsley was arrested and later sentenced to life imprisonment with a recommendation that he should never be released. He was sent to Broadmoor Hospital for the criminally insane. In 1977, Maudsley and another inmate, David Cheeseman, took a third patient (a convicted child molester) hostage and locked themselves in a cell with their captive, before torturing him to death over a period of nine hours.
After this incident, Maudsley was convicted of manslaughter and sent to Wakefield Prison. He disliked the transfer and made it clear he wanted to return to Broadmoor.
One afternoon in 1978 he killed two more fellow prisoners. Maudsley's first victim of the day was Salney Darwood, a murderer convicted of the manslaughter of his wife. Maudsley had invited Darwood to his cell, where he garrotted and stabbed him before hiding his body under his bed. He then attempted to lure more fellow prisoners into his cell, but all refused.
Maudsley then went on the prowl around the wing hunting for a second victim, eventually cornering and stabbing prisoner Bill Roberts to death. He hacked at Roberts' skull with a makeshift dagger and smashed his head against the wall. Maudsley then calmly walked into the prison officer's room, placed the dagger on the table and told him that the next roll call would be two short.
In 1983, Maudsley was deemed too dangerous for a normal cell. Prison authorities built a two-cell unit in the basement of Wakefield Prison to house him for the continuation of his confinement. Maudsley is housed in a 'glass cage', a two-room unit that resembles the one featured in the Hannibal Lecter film Manhunter. It was built for Maudsley seven years before the film was released. At around 5.5 m by 4.5 m, the two cells are slightly larger than average and have large bulletproof windows through which inmates can be observed.
The only furnishings are a table and chair, both made of compressed cardboard. The lavatory and sink are bolted to the floor while the bed is a concrete slab.
A solid steel door opens into a small cage within the cell, encased in thick Perspex, with a small slot at the bottom through which guards pass him food and other items. He remains in the cell for 23 hours a day. During his daily hour of exercise, he is escorted to the yard by six prison officers. He is not allowed contact with any other inmates.
In March 2000, Maudsley unsuccessfully pleaded for the terms of his solitary confinement be relaxed, or to be allowed to commit suicide via a cyanide capsule. He also asked for a pet budgie, which was also denied.
In 2010, Maudsley made a plea to be able to play board games with prison staff to relieve his boredom in solitary confinement.