It was one of the most controversial police operations in British history. In the early 1990s, Rachel Nickell was brutally murdered in front of her two-year-old son. Her body was found with her child still clinging onto her. To catch the man the police supposed was the killer, they authorised Operation Edzell, a “honey trap” with an undercover female officer faking a relationship with the suspect for months to discover the truth.

It is this unsettling story that the new four-part Channel 4 drama takes up, uniquely told from the perspective of the undercover officer herself, played by The Virtues’ Niamh Algar. It deals with the brutal human cost of the case and the long-lasting impact these extreme measured had on all involved – and what it truly means to lose your identity for the grim and dangerous purpose of baiting a suspected killer.
 

Set against a backdrop of heightened sexual politics and second-wave feminism in Thatcher’s Britain, it’s a hugely affecting series, as Algar’s character – codenamed Lizzie James – sinks deeper and deeper into the dire situation she has been placed, growing increasingly isolated and vulnerable, as she tries to win the trust of the apparently unstable Colin Stagg (Sion Daniel Young, Keeping Faith). Algar’s performance is by no means an easy watch – but it is an important one.

“We need to look back at these moments, otherwise we don’t understand what went wrong,” says Dave Nath, executive producer on the show. In the real case, the undercover officer ended up living with Stagg for five months, claiming that she had murdered someone to win his trust and get him to confess to Rachel’s murder. Rochenda Sandall (Line of Duty) plays her colleague Lucy, while Nathaniel Martello-White (I Hate Suzie) plays her sometime confidante, Baz.
 

Niamh Algar plays the undercover officer in an astonishing performance

As you’d expect in a series that depicts one of the biggest murder enquires this country has ever seen, there are many moments in the show (which was produced by combing through previously unheard audio, video and written materials, as well as using scenes of verbatim dialogue) where you struggle to take in the horror of the situation. But for series star Algar, it was a phone call with her character’s mother that was the hardest to film.

“You see her very much stripped bare,” she says. “She’s someone who’s remarkable at her job but having to put this mask up. In that scene, she’s someone’s daughter, and during the conversation comes to realise she doesn’t really know who she is anymore.”

The series continually plays with this idea of identity and truth, but also the why this ill-fated operation happened in the first place. “In hindsight now, you can see where the markers were, what choices were made that led [the operation] in the wrong direction,” says Harry Treadaway (The Crown), who plays Keith Pedder, the relatively young and inexperienced Detective Inspector leading the case.
 

Harry Treadaway, previously seen as Roddy Llewellyn in The Crown, plays the inexperienced and under-pressure DI Keith Pedder

“The hysteria and panic around a crime like this, which is generated in part by media attention, it skews people’s judgment,” adds Nath. “When Keith Pedder is getting squeezed by bosses and having journalists turning up at the police station, you’ve got to feel that, to know the context and pressure of the situation.” 

Indeed, this was a horrific murder that shocked the country at large, and the pressure on the police force to find the culprit was intense. Not only because they wanted to bring the person who committed the atrocious act to justice, but the media at the time were feeding a national obsession, with every detail on the case splashed across front pages.

There was also a very real fear that the killer, still at large, would soon strike again.
 

Sion Daniel Young plays the suspected killer, Colin Stagg

During the initial investigation, the police interviewed 32 men in connection with Rachel’s murder, but without progress. As circumstantial evidence started to point towards Stagg, following a BBC Crimewatch appeal, Peddler engaged the nation’s most famous criminal profiler, Paul Britton (Eddie Marsan, Ray Donovan) to help devise the undercover sting to land the crucial piece of the puzzle that – they think – will solve the case.

As for what happens next, you’ll need to tune in to find out. Because no matter how shows like Line Of Duty portray the fictitious world of policing, the reality here is far stranger – and far more disturbing.

When is Deceit on TV?

Deceit airs on Channel 4 HD (CH 104/141) on Fridays at 9pm, with the first episode screening on 13 August. It is also available in Apps & Games > All 4.

The four-part series will subsequently air every week until Friday 3 September.