Cannibal Killer (five, 10pm); Nigella Express (BBC2, 8.30pm)

DESPITE a thorough job in detailing the horrific crime of Darlington's Cannibal Killer, this documentary remains unable to answer vital questions.

What did David Harker, a man who boasted of wanting to become Britain's youngest serial killer, do with the head and limbs of his victim?

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And did he really, as he boasted, cut off part of her thigh and cook it with garlic butter and pasta? Police have never found any evidence to confirm that, just as all efforts to find the missing body parts have come to nothing.

The Northern Echo and reporter Karen Westcott have a part to play in this horror story about the mother-of-four butchered by Harker. Friends of both the victim, Julie Paterson, and the killer talk about their relationship with the key players in the crime.

Her boyfriend, Alan Taylor, never recovered from the murder, searching endlessly for Julie's missing body parts before killing his best friend and eventually himself while in prison. He's shown at her graveside asking: "How can she be at rest, she's not even all there."

The moment when police found the missing women's torso is vividly recalled by Detective Inspector Ian Phillips, who tells of waiting for first light to investigate a sack found in the undergrowth in a residential area of Darlington.

He knew the contents wouldn't be pleasant because of the smell. "You could clearly see on the top of the sack the shoulder blades of a human being," he says.

The trail led to David Harker, who'd told more than 20 friends that he'd chopped up Julie, dumped the body, and put the head and limbs out with the rubbish. Nobody believed him. By the time police interviewed him, he denied the murder, despite forensic evidence at his home linking him with the dead girl.

Harker may have talked of eating his victim to enhance his reputation. He also claimed to have killed two other people, although the police never substantiated this.

He may just have sensationalised what he'd done to gain notoriety.

He began a letter-writing campaign to The Northern Echo in which more outrageous allegations were made. He also talked of HORROR STORY: David Harker, Darlington's Cannibal Killer, boasted that he'd eaten parts of his victim, but police think he was fantasising necrophilia and creating masks out of the skin of his victims, at which point police concluded he was fantasising using scenes from movies.

A psychiatrist views Harker as a typical psychopath who's also a sadistic killer. As for Harker himself, he wrote in one of the letters to The Northern Echo: "I am not evil, I am a monster".

Detective Chief Inspector - now Chief Superintendent - David Jones reports that Harker has kept his silence and refused to see any visitors. Before the police officer retires, he intends to visit Harker and ask what he did with the rest of Julie Paterson's body.

The story is gripping enough without embroidering it with dramatic talk of "the horror story that shook the quiet town of Darlington", and is Darlington really "a sleepy town" as described by the narrator? We get quite enough of that sort of careless talk from Nigella Lawson in Nigella's Express, which features two "yummy get-ahead suppers" this week.

Fans of Nigella can hear her get her tongue saucily round words and phrases like squodge, whirr and whips. By the time she's talking of her "golden mound of liquor-sodden sponge" you'll be in seventh heaven.

Her passion fruit and ginger trifle is a mere trifle compared to her chocolate ice cream cake with butterscotch sauce (not poured but drizzled over the top).

To plain vanilla ice cream she adds bourbon biscuits, chocolate covered honeycomb, honey roast peanuts... at this point, she can hear people complaining about all the sweetness. "You might as well stop worrying about the sugar content, it's a bit of a waste of time," she says, adding chocolate and peanut butter chips to the mixture.

Her supper guests love it. "Nothng succeeds SCRUMMY: Nigella Lawson tucks in like exccess," grins Nigella.