'Until I Kill You' tells the true story of a woman who unwittingly dated a murderer. What to know about David, the partner who supported her.

• "Until I Kill You" is about Delia Balmer, who was in a relationship with the serial killer John Sweeney.
• Sweeney testified against Balmer after he attacked her, and she was supported by her new partner, David.

True crime drama "Until I Kill You" tells the story of Delia Balmer (Anna Maxwell Martin) and her relationship with the serial killer John Sweeney (Shaun Evans).

When they started dating in 1991, it was unknown to Balmer that Sweeney had murdered his ex-girlfriend Melissa Halstead. Her remains were found in a Rotterdam canal in 1990. Sweeney went on to kill another woman in 2000. The police suspect that he killed three other women between the late 1970s and the late 1980s, but were unable to prove it.

Sweeney attacked Balmer with an axe outside her London home in December 1994 and then went on the run for six years. Police caught him in 2001.

After the attack, Delia moved to a new house in a different part of London, where she started a relationship with a local taxi driver called David (Kevin Doyle).

In the show, the relationship lasts for around four years, and David provides her with safety and security while she testifies against Sweeney in court over the attack.

"Until I Kill You" follows other buzzy true crime dramas of 2024, including "Baby Reindeer," "Under the Bridge," and "Monsters."

The show, which was produced by the British network ITV, highlights the challenges faced by victims of domestic violence who seek justice.

Kevin Doyle said the version of David in "Until I Kill You" was "diluted slightly."

Doyle said that David was based on a real person Balmer was with during the early 2000s.

He said the director Julia Ford wanted David to be the exact opposite of Sweeney.

He said: "I'm not one of those actors who does a great deal of research if it isn't necessary and I didn't feel it was in this case, so I didn't find out lots more about David, but Julia set me straight on what she saw in the character.

"She said she wanted there to be something very calm and reassuring about him, and nice — she wanted as big a contrast as possible to the darkness Shaun was bringing as Sweeney."

Doyle said the character is different to the real-life version of David.

He said: "There are aspects of David we diluted slightly, like the fact he was a very heavy smoker, but nevertheless Delia found comfort in the stability that David offered and he did seem to offer something loving.

"He was very generous with his time and his money, but nevertheless, she just couldn't fully commit to the relationship, and they lasted three or four years together."

The real David also encouraged Balmer to testify against her attacker, but the actor said that this prompted the end of their relationship.

He said: "He is absolutely supportive of Delia all the time and he is very keen to see Sweeney put away. That was actually the beginning of the breakdown of the relationship because he wanted her to get fully involved in the police's attempt to imprison Sweeney, but she just wanted to back away from it and get on with her new life.

"He didn't insist on it, but he was always suggesting it would be the better route for her in the long term and she reluctantly went along with that in the end."