John Sweeney showed gruesome sketch to his son who recalls 'haunting' experience

ITV's series, Until I Kill You, takes its inspiration from the harrowing experiences of John Sweeney's only known surviving victim, Delia Balmer. Portrayed by Anna Maxwell-Martin, the character of Delia unearths a chilling collection of Sweeney's artwork depicting decapitated women and other macabre scenes.

The true story saw Sweeney evade capture for six years following a near-fatal assault on Delia. His eventual arrest led to a conviction for the murders of two women, with police discovering a horrifying array of his artworks during the investigation.

Amongst these finds was a scratchcard with a poem written by Sweeney about Melissa Halstead, his first girlfriend and murder victim. The grisly verse read: "Poor old Melissa, chopped her up in bits, food to feed the fish, Am*dam was the pits."

In one particular painting titled One Man Band, an image of a woman, believed to represent Melissa, concealed something more sinister. A coating of correction fluid hid an area that, when exposed under ultraviolet light, showed a gravestone bearing the inscription: "Melissa Halstead, born 7 November 1956. Died."

A striking disclosure came from Sweeney's son Michael, who recounted a disturbing moment from his youth when his father presented him with a sketch of Michael's mother in a coffin, inscribed with 'Rest in Peace Ann', reports the Mirror.

Initially, Michael, who has a sister named Tracey, perceived it as merely his father's expression of bitterness after the collapse of their parental relationship.

Upon Sweeney's conviction for double murder, Michael grasped the eerie reality of the unnerving picture.

Speaking in an earlier article with the Mirror, he recounted: "I could see it was my mum straight away. It was so lifelike. It was like a photograph."

"I thought at the time it was strange but just a symbol of their bad relationship. Now I know he has killed I can't help but wonder, 'Why didn't he kill my mum?'"

Michael articulated his concerns that his father might have more unnamed victims and felt compelled to speak out to give both his own family and the victims' families some closure.

He confronted his dad about whether the sketch depicted Ann, receiving only a simple "yes" and witnessing his father's reclusive behaviour.

In the run-up to Ann's death in 2002, Sweeney had penned a letter declaring his enduring affection. "He was obsessed with her. I think they were married twice and divorced twice," said Michael.

Serving a life term now, Sweeney is a figure Michael shows no desire to encounter again.

Their paths crossed briefly at a familial funeral, which Michael called "quite haunting".

Ann had attempted to avoid Sweeney, yet for a period, he persistently pursued her.

Until I Kill You continues on ITV at 9pm