A prison warden has been suspended over an alleged affair with a West Croydon murderer responsible for sexually assaulting and battering a care worker to death.

The unnamed woman is believed to have slept with 27-year-old Leigh Thornhill – described as “dangerous and perverted” by a judge – at Wakefield prison.

The Prison Service confirmed it was investigating the incident at the high security jail, which holds some of Britain’s most dangerous prisoners.

Thornhill, who was thrown out of the Army because he was “unsuitable for the military”, was just 19 when he was caged for life for sadistic attacks on two women.

The Old Bailey heard Thornhill battered a mother-of-two to death in the early morning in August 2003.

Corinne Bailey, a care worker, was found lying in a pool of blood near Thornhill’s home.

She had been sexually assaulted and received 68 separate injuries after being battered with a plank of wood.

Hours before the horrific murder, Thornhill attacked Julie Francis in London Road to pay for sex.

When asked for payment upfront, he strangled her until she lost consciousness. The Old Bailey heard when she came around, she screamed for help and a group of men came to her aid, chasing Thornhill, who escaped.

Two hours later he attacked Mrs Bailey with a plank of wood as she walked down Campbell Road after buying cigarettes and a newspaper.

The court heard he had spent the evening drinking in pubs and clubs in Croydon.

After the trial, he was also linked to a sexual assault on a woman eight months previously.

He was arrested and interviewed in connection with a December 2002 attack on a 21-year-old in Selsdon Road.

She was clubbed over the head with a metal bar and sexually assaulted, sustaining serious injuries to her head and arms.

A spokesman from the Prison Service said: “A member of staff from HMP Wakefield has been suspended pending the outcome of an internal investigation.”