The shocking true story behind ITV's Until I Kill You and killer John Sweeney

ITV’s new drama Until I Kill You tells the horrific story of the life of serial killer John Sweeney, his victims, and his one known survivor - Delia Balmer.

The four-part true-crime series began over the weekend and continues again on Monday night.

John Sweeney, played by Shaun Evans, was convicted of murdering two women - Melissa Halstead and Paula Fields. He was dubbed the Canal Killer as he threw the bodies of his victims into different canals.

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Delia Balmer, played by Anna Maxwell-Martin, was a former girlfriend of John Sweeney who managed to survive an almost fatal attack in 1994, four years after they got together.

The real Delia Balmer wrote a book about her experience living with a serial axe murderer, called Living With a Serial Killer. ITV’s new series draws its narrative from this book.

The chilling true story unfolds in 1991 when Delia was employed as an agency nurse in London. She met John Sweeney in the pub and although their initial meeting didn't lead anywhere, they crossed paths again weeks later on the street, reports the Mirror.

Sweeney asked Delia out, and although she initially declined, his persistent advances led her to write him a letter and they ended up in a relationship.

After enduring two years of an abusive relationship, she finally mustered the courage to ask him to leave in December 1993. However, he continued to manipulate and control her, with things escalating in the spring of 1994 when he held her hostage in her own home for several days.

He bound her to the bed and threatened her with a gun and knife, warning her not to scream. During this horrifying ordeal, he