An ITV documentary broadcast this evening (September 1) will show the steps that led to Chester women Sarah Williams and Katrina Walsh being found guilty of a shocking murder.

On August 17, 2016, Williams and Walsh were convicted of murdering of Sadie Hartley.

The Murder of Sadie Hartley tells the gripping story of how detectives solved the case.

Detailing everything from the first call to the crime scene through to the convictions of the vicious killers, viewers are given extraordinary access to the multidisciplinary police operation.

The dawn raid and arrest of Sarah Williams was filmed by a TV crew

Filmmakers were there though every step as Lancashire Police investigated the violent stabbing to death of the businesswoman at her home in January 2016, unpicking a crime committed with what prosecutor John McDermott QC described as ‘demonic savagery’.

Steve Warr, executive producer for Raw Cut TV, said: “We were privileged to get the inside story of the investigation into who killed Sadie and the story that evolved is stranger than any crime drama.

"How these detectives hunt down the two women at the heart of the murder is utterly compelling and the most complete and gripping picture of a real life crime being solved I have ever seen.”

Police near the scene after mother-of-three Sadie Hartley, 60, was murdered in a 'ferocious' knife attack at her home in Helmshore, Lancashire

Sadie's daughter Charlotte, 23, also appears in the film.

Cameras follow detectives as the case unfolds from the crime scene to the dawn raid in which key suspect Williams was arrested, and the moment the murder weapon and other key evidence is discovered and ultimately to the arrest and conviction of the key suspects.

As lead Detective Superintendent Paul Withers and his team including Detective Bryony Midgley piece together evidence, they discover that Sarah Williams, who enjoyed a tangled web of relationships with multiple lovers including a 75-year-old 'sugar daddy' and Sadie’s partner, former fireman Ian Johnson, considered herself Sadie’s love rival.

Sadie Hartley's children Harry and Charlotte outside court

The police also unravel lies told by Williams and discover her accomplice, Walsh, who claims to have no memory of the crime.

Yet evidence showed the pair hatched an 18-month-long plan to kill Sadie involving scouting her house, visiting Germany to buy a key weapon, and even buying a second-hand car in a bid to evade detection and pull off the perfect murder.

The Murder of Sadie Hartley follows the case over 90 minutes, telling the compelling story of a dark and tragic crime that left family members searching for answers.

The Murder of Sadie Hartley airs this evening (Thursday, September 1) at 9pm on ITV.