For 10 months mum-of-five Janet Leach was forced to listen to some of the most gruesome murder confession in British history.

Her harrowing story inspired the ITV drama, Appropriate Adult, after she spent more than 400 hours locked in a sell with serial murdered Fred West as he was questioned by police.

Janet was doing social work when she volunteered to become an appropriate adult - someone who is asked to sit in with often youngsters who don't have a parent with them when they are interviewed by police.

Her role was to ensure justice was being served but she could never have imagined that a single phone call who lead to a living nightmare.

On February 25, Janet was called to the police station for the questioning of a 52-year-old man with learning difficulties. That man was Fred West.

Fred West was responsible for at least 12 murders
Fred West was responsible for at least 12 murders

She had to spend hours alone with the killer, who is responsible for the deaths of at least 12 people, along with his wife, Rose, who was convicted of 10 murders.

During their time together, Janet says Fred began to trust her and revealed his twisted crimes in disturbing detail.

Twisted pair Fred and Rose West carried out their murder spree over 20 years and even killed their own daughter, Heather.

They would often lure their victims back to their home in Cromwell Street, Gloucester, where they would be tortured before they were murdered.

Horrifyingly, many of the victims were buried in the couple's garden and even in the walls of their home, which was dubbed the 'house of horrors'.

Fred with his killer wife, Rose
Fred with his killer wife, Rose

Ultimately, it would be Heather's death that led to Fred and Rose West's capture when police searched their home while investigating the teenager's disappearance.

The crimes appalled the country but for Janet there was no escape as she was forced to listen as Fred unburdened himself during their meetings.

She says he would also call her several times a week with more information.

Janet said: "Fred would tell me these horrible things as if he was discussing the weather."

His boasts horrified the devoted mum. She said: "We used to go round to children's homes for some of them. We would give them a good time and they all enjoyed the sex. We used to tie them up. Some suffocated, we did not mean to kill them but we did.

Fred took his own life in prison
Fred took his own life in prison

"Some were hung up like pigs and their throats were slit. There was blood everywhere. We used to hang them up and leave them there."

After months of keeping the horrifying details of what she had been told by the killer secret, Janet told her story to the Mirror but was then called to give evidence at Rose's trial, something she says she had been assured she would not be called to do.

However, as she was being cross-examined about her deal with the Mirror, Janet suffered a devastating stroke in the witness stand.

Up until Fred's suicide, she had regarded his sick secrets to be as private as the priest's confessional because "he told me the truth would come out at the trial". Now she told the police.

Janet said at the time: "I could not cope with the things he was telling me but I felt I had to carry it through even though I hated it.

"I wanted to get the bottom of how many victims there were for the sake of the families.

"I could not bear the thought that there was a child buried out there who would not be discovered because I had not listened to what he had to say. I will be haunted for ever by the things he told me. Now I wish I had never taken that 4pm phone call from the police.

"He did tell tales - some hard to believe. But you could not dismiss anything he said because the graves that were discovered were on his information alone."