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 confessed to murdering his ex-girlfriend, Melissa Halstead, revealing that he had disposed of her body in an Amsterdam canal.

After seven days of captivity, Sweeney finally released Delia and allowed her to return to work. Later that year, Delia sought help from a women's refuge and informed the police.

Despite reporting Sweeney, the authorities did not take significant action and he committed two further attacks on Delia that year. When she failed to show up for an appointment with a friend, the concerned friend contacted the police. The police discovered a bag containing Sweeney's murder kit and they arrested him.

A week later, he was released on bail under the condition that he returned to his parents' home in Skelmersdale. But he violated his bail conditions and went back to Delia's home, where he carried out an almost fatal attack.

A neighbour intervened after being alerted by the nose, Sweeney fled and Delia was rushed to hospital.

After this, Sweeney managed to evade capture for six years before his location was discovered. Under the alias 'Joe', he returned to London where he met Paula Fields, whom he murdered in December 2000.

The Metropolitan Police launched a murder investigation.

The murders of Melissa and Paula were linked in February 2010 and Liverpool-born Sweeney was arrested at Gartree Prison in Leicestershire, where he was serving life for an axe attack on Delia.

The former carpenter, 67, is still in prison, where he is likely to remain for the rest of his life.

He had refused to leave his prison cell at Belmarsh prison to hear his sentence after he was found guilty of the two murders.

Police confiscated more than 300 pieces of Sweeney’s artwork, many of which depicted his horrific crimes. Ultimately, it was this artwork that provided the crucial evidence police needed to link him to multiple murders, leading to his life sentence.

The full series of Until I Kill You is available to stream now on ITVX. The next episode of will be broadcast on ITV1 at 9am on Monday.