Until I Kill You: the terrifying true story behind ITV’s new true-crime drama

ITV’s latest true-crime drama, Until I Kill You, tells the terrifying true story of nurse Delia Balmer, who survived a near-fatal relationship with serial killer, John Sweeney.

Anna Maxwell Martin and Shaun Evans star in the four-part series, based on Delia’s 2017 memoir Living with a Serial Killer, which follows the pair’s relationship, from their first meeting in a London pub in 1991 to when he attacks her with an axe. The story tells of Delia’s traumatic journey through the police and criminal justice system as they attempt to send John down for his crimes. 

But what exactly happened between Delia and John? Keep reading to discover the horrifying true story behind the series. 

Delia’s relationship with John Sweeney

Delia and John first met in a pub in Camden, north London in 1991, when nurse Delia was in her early 40s and had just moved to the UK from America, where she grew up. 

The pair hit it off, bonding over their shared love of travelling, and their relationship quickly progressed as they moved in together. 

John would shower Delia with gifts, affection and flowers. But his behaviour soon turned coercive and controlling as time went on. 

John’s attack after 3-year relationship with Delia

While Delia admits she was “too soft and trusting” in the beginning, she eventually asked him to move out and ended their relationship in 1994, changing the locks and asking the police to investigate a suspicious bag hidden away in the bathroom. In her memoir, she describes the bag as “a body disposal kit meant for me“.

John then broke into her home, tied Delia up and held her hostage for four days. During this time, he confessed to the murder of his ex-girlfriend, American model Melissa Halstead, who went missing in 1986 and whose remains were later found mutilated in a canal in Rotterdam.

When John left the flat and released Delia, she went to the police. While they arrested him for false imprisonment and ABH, after finding the “body disposal kit” in the bathroom, he was later released on bail. 

On 22 December 1994, Delia returned home from her last shift before Christmas, the day after John was released, to find him waiting for her with an axe. 

John attacked Delia and cut off one of her fingers before one of her neighbours saved her life by hitting John with a baseball bat. She also suffered a broken arm and torn tendons. 

John made his escape and went on the run.

John’s capture and sentencing

Six years later, John was arrested and handed a life sentence for Delia’s attempted murder. 

Then in 2010, John was charged with the murder of Melissa Halstead and 31-year-old mother-of-three Paula Fields, who he had killed while on the run. Her body was found in Regent’s Canal in 2001.

After Delia testified against John in court, he was found guilty of both murders and given four life sentences for his crimes. 

At the time of John’s sentencing in 2011, the Metropolitan Police said the force was still trying to trace three unidentified missing women, who detectives believed may have been ex-girlfriends of John: a Brazilian woman named Irani, a Colombian woman called Maria and a British woman named Sue. 

In an interview with The Guardian, Nick Stevens, who penned the ITV drama, revealed that Delia still sleeps in the bed she was tied to when John held her hostage.

“Amazingly, Delia still sleeps in the bed Sweeney made for her and to which he tied her for four days. I can’t be sure how she processes all this. But I’m certain she’s in a better place than she was,” explained Nick, who also said that he and his wife regularly take Delia out to a Greek restaurant in London. 

Did actors Shaun Evans and Anna Maxwell Martin meet Delia?

While Anna met Delia shortly before filming ended, Shaun never met her. 

Explaining her decision not to contact Delia, Anna told The Guardian: “I can’t really say why, I just never have before when I played real people. You are studying people, their mannerisms and so on. If you were sat in a room with them, you might end up staring at them in a fairly weird way. For this, I watched tapes of Nick Stevens interviewing her, which was really useful.”

She went on to add: “I knew Delia would find it challenging to see herself wrenched to life by a semi-bad actor. And she was very game and funny about that.”

Meanwhile, Shaun said he “purposefully and respectfully” decided not to meet Delia or anyone connected with the case. “I never met Delia or anyone connected with the case. I started to read the book then put it down because I didn’t want to see the story exclusively from Delia’s point of view,” said the actor. “There were moments on set when you’d think: ‘Bloody hell, this actually happened!’ But I found I had to put that aside.”