Is Until I Kill You based on a true story? Everything you need to know about Delia Balmer and John Sweeney

Until I Kill You tells the extraordinary true story of Delia Balmer who almost died after forming a relationship with murderer John Sweeney.

Until I Kill You is set to air on ITV from November 3 and the four-episode series will be followed by a companion documentary Until I Kill You: The Real Story. Anna Maxwell Martin stars as Delia Balmer, with Shaun Evans playing John Sweeney.

The real Delia Balmer went on to write a book about her experience living with a serial axe murderer, called Living With a Serial Killer. The series is based on what is written in this book.

The horrifying true story began in 1991, when Delia was working as an agency nurse in London. At 40 years old at the time, she lived alone and led a solitary life.

She met a man at a pub, who was four years younger than her, and introduced himself as John Sweeney. Nothing came of their initial interaction but weeks later, they bumped into each other again on the street.

Sweeney asked Delia out and she initially said no, but after further advances from him, she decided to write him a letter - a decision she would come to deeply regret.

Sweeney had been working as a casual labourer and was living in a squat, so he was very keen to move into Delia's home.

Delia recalled how he would have raging outbursts of anger and she was keen to get rid of him but was scared to ask him to leave.

After two years in an abusive relationship, she finally plucked up the courage to ask him to leave in December 1993.

However, he continued to manipulate and control her and things came to a head in the spring of 1994, when he held her hostage in her home for days on end.

He tied her to the bed and threatened her with a gun and knife, saying he would cut her tongue out if she screamed.

It was during this time he admitted to killing his ex-girlfriend, Melissa Halstead, saying he cut her body up and threw it in a canal in Amsterdam.

After four days of keeping Delia tied up, Sweeney finally released her and let her go back to work.

Yet the terrorising continued and in July 1994, Delia sought help from a women's refuge and police were informed.

However, they did not act much on the initial reports, leading to two more attacks on Delia that year.

Even after changing the locks on her home, Sweeney broke in and abused her, holding her captive for another day.

After she failed to attend an appointment with a friend, the friend called the police who went to Delia's home and found a bag containing tarpaulin, masking tape, surgical gloves, and rope - Sweeney's murder kit.

A week later he was released on the condition he returned north to his parent’s home in Skelmersdale. condition he returned to his parent’s home in Skelmersdale.

However, he broke bail conditions and went to Delia's home, where he carried out the almost fatal attack.

It was December 22, 1994, and as Delia returned home from work on her bike, she saw Sweeney approaching her outside.

He swung an axe which hit her in the arms and then stabbed her in the breast and thigh with a knife.

A neighbour heard the commotion outside and hit Sweeney with a baseball bat, causing Sweeney to flee and Delia was rushed to hospital.

She miraculously survived, but was left with many physical and emotional scars.

Sweeney went on the run for six years before his whereabouts became known again.

He returned to London using the name Joe and went on to meet Paula Fields, before murdering her in December 2000.

The Metropolitan Police opened a murder enquiry and identified Paula’s body by DNA. Sweeney was caught by police and he was carrying a gun and a knife.

Police seized over 300 pieces of his artwork which depicted his gruesome murders.

In the end, it was Sweeney's artwork that gave police the evidence they needed to connect him to multiple murders and he was sentenced to life in prison.

Until I Kill You airs on ITV from November 3