John Sweeney's harrowing murder confession to girlfriend Delia Balmer that left her 'astounded'

Delia Balmer remembers the chilling moment confessed to his crimes while waving a knife in the air.

Agency nurse Delia was 40 years old when she met Sweeney, an artist and carpenter, in a pub in Camden, North London, back in 1991. The couple bonded over their love of travelling and before moving in together. But she soon became suspicious that her lover was hiding a sinister secret.

ITV's new drama, - starring Bafta-winning actress Anna Maxwell Martin - is based on Delia's memoir, in which she recounts her violent relationship with the notorious serial killer. In her 2017 book, Delia tells of the moment she discovered her boyfriend was not who he initially seemed, and how it made her feel.

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Delia embarked on a three-year relationship with Sweeney, but things turned nasty after she ended it in 1994. The nurse became alarmed after finding rope, tape and gloves hidden under the bed they shared, and then learned the terrifying truth. Sweeny held her captive for four days, repeatedly raping her before attempting to kill her with a wooden axe.

Miraculously, Delia lived to tell the tale and see her former partner put behind bars for the attempt on her life and for the double murder of two of his ex-girlfriends. In 2011, he was sentenced to life imprisonment without the possibility of parole. It's believed he could have killed three other women who were reported missing between 1970 and 1990.

In her book, Living With A Serial Killer, Delia recalls the moment Sweeney confessed his crimes to her. She writes that he told her, referring to American model and photographer Melissa Halstead, and ranting and raving as he spoke: "We were in our room in Amsterdam... Melissa was there, and there were two German guys." What he said next 'astounded' her.

"I killed them all," Sweeney said. "I sat with the bodies for three days. I didn't know what to do; I didn't want the police to find me." She remembers him waving a knife in the air, 'slicing through it, the blade swishing left and right'. "On the third day," Sweeney continued, "I cut up their bodies, and put them in bags, and threw them in the canal."

After being careful not to anger Sweeney further, Delia managed to survive her hostage ordeal, while he fled the flat. She reported him to the police and he was sent to North London's Pentonville Prison, only to be released on bail. It was then that Delia experienced a devastating premonition.

Speaking with the in 2017, Delia said: "I thought: 'He will do something. He will cut me to bits. Just like he had Melissa'. The moment I discovered he was out, I was on edge. I knew he would be coming for me." Horrifyingly, her gut feeling proved all too accurate. Shortly before that year, Sweeney attacked Delia with an axe on her own doorstep.

He punctured her lung, broke both her arms and stabbed her in her breast and thigh. He also cut off her little finger, which Delia recalls seeing 'flying through the air'. Thankfully, Delia survived the attack after a neighbour intervened and Sweeney fled into the night. This would be the last she'd see of him for seven years. In 2001, he was finally caught and arrested.

The national domestic abuse helpline offers support for women on 0808 2000 247, or you can visit the website. There is a dedicated on 0808 8010 327.

• You can catch Until I Kill You: The Real Story this evening (November 7) at 9pm on ITV1.