PREVIEW: Deceit, Channel 4

Four-part drama based on a true story. Deceit examines the controversial honeytrap at the heart of the high-pressure investigation into the devastating murder of Rachel Nickell, a young mother brutally attacked in front of her two-year-old son on Wimbledon Common in London in 1992.

Fuelled by incessant media headlines and public interest, there is a climate of fear and a national obsession with catching the killer before he strikes again. The police are under enormous pressure, and criminal profiler Paul Britton (Eddie Marsan) and Detective Inspector Keith Pedder (Harry Treadaway) devise a highly unique and dangerous undercover operation fronted by an ambitious female officer, 'Sadie Byrne' (Niamh Algar).

Based on only circumstantial evidence, she is tasked with forming a relationship with the prime suspect, a self-confessed lonely man who lives close to the scene of the crime, by the name of Colin Stagg (Sion Daniel Young). If Sadie can win his trust, they believe he may disclose his involvement in Rachel's murder.

Carefully guided by the criminal profiler, Sadie adopts the persona of 'Lizzie James', a woman with a dark secret in her past, and is tasked with becoming sexual bait to trap an innocent man. And so begins one of the most controversial operations in Met Police history. Co-starring Rochenda Sandall and Nathaniel Martello-White.

The whole series will be available on All 4, to stream or download for free, following transmission of this episode on Friday 13 August.