In July 1992 a young woman called Rachel Nickell was murdered while walking on Wimbledon Common with her two-year-old son, Alexander.

Police were convinced that a local man, Colin Stagg, was responsible for her murder, but weren’t able to prove it. So, they bought in Sadie (a fictional name,) an undercover police officer given the codename ‘Lizzie James’, to entrap him. 

The case’s lead, Detective Inspector Keith Pedder, along with a forensic profiler, drew up a profile of Stagg, and they then coached ‘Lizzie’ through a satanic backstory that they believed would appeal to his criminal tendencies, and cause him to confess to the crime.

The story has been made into a powerful four-part drama premiering on Channel 4 tonight, with a focus on Sadie, the woman at the heart of the operation (played by Irish actor Niamh Algar). It looks at what she endured as she went through the case – including having to write Stagg violent and explicit letters, talking to him regularly to develop a ‘relationship’ and meeting the man they believed to be a murderer face to face.

When another woman, Samantha Bissett, and her young daughter, Jazmine, were murdered, it finally emerged that Stagg was innocent of Rachel Nickell’s death. He was released from prison after 13 months on remand, and it was proven that both crimes were committed by a man called Robert Napper. 

While Stagg was given freedom following this miscarriage of justice, the legacy of what Sadie had to go through meant she left the force and was given lifelong anonymity.

We spoke to Algar about taking on this remarkable story and the importance of centring the female experience in it. 

Stylist: What was it that captured your attention about this particular drama?

Niamh: It was a unique perspective that this woman had on this case and that I was not aware of. I was familiar with the Rachel Nickell murder, but I wasn’t aware of the woman who was placed undercover. I had so much admiration for Sadie, and women in that job: the bravery of doing undercover work, the situations in which they would have to go. That strength she imbues in the character was very unique and something I hadn’t seen portrayed before.

It’s not often we see cases like this through the eyes of a woman, rather than the perpetrator of the crime. What’s the significance of that?

It was really important for a story like this to be told from the perspective of Sadie’s character. I think, for a woman in the early 90s, in this job, she’s very much a woman in a man’s world, trying to hold her own in a situation where she has to be both vulnerable and strong at the same time. You have to show the vulnerability of a character in order for the audience to see how exposed she was: she went to meet who she thought was Rachel’s killer, unarmed.

We chose with this character that she would be very isolated: she is incredibly lonely and it was important to show how that might have an emotional effect on a person. For me playing this character, especially during the lockdown, every night [after filming] I would have to sit with the day and digest the scenes and emotions. 

I spoke to a few officers who have done this job to get a sense of how those women dealt with everyday life doing a job like this – I didn’t speak directly with Sadie, to protect her identity. One said to me: you create your character, but while for you, as an actor, if you mess up the line, you get to go again. If I mess up my line, I could end up getting hurt. That put goosebumps on my arm, about how brave these women were.  

In one scene they describe what Sadie is doing as ‘acting as bait’ which I found quite a dehumanizing way to speak about someone putting themself on the line to catch a criminal…

Playing that character, I never saw her as someone who was bait. I saw her as someone who is in control, she has to be in control of her own fate and destiny and maybe she doesn’t realise there and then just how serious the situation was. When I spoke to some of the women, they said that information would sometimes be withheld about how dangerous an operation they would be going into so they wouldn’t be overwhelmed by the fear. It is interesting, on watching now, just how exposed and vulnerable she is, but I never saw her as being vulnerable.

You also see her descent, and how the case impacts her wellbeing. I felt like there was a lack of duty of care. The parts where she had to read out the sexually explicit letters she wrote to Stagg were particularly uncomfortable. Was that something you felt?

The series is exploring the idea that she didn’t exactly have the best support. There is, I suppose, a fear that if she felt like she appeared weak that they would think that she’s not ready for this operation, given that this is the biggest operation the Metropolitan Police had in history. And the fact that a woman was the centre of this is a massive opportunity. The level of pressure that she was under was enormous; I can’t imagine how tough that must have been. 

There seems to be so many victims in this case, who do you think deserves our sympathy?

When you look at it as a whole, everyone is a victim in a way: Colin is a victim. Audiences can see for themselves where things have fallen.

And what was the responsibility you felt in telling this story?

For me, it was making sure that I was representing the character, from my research, as truthfully as possible in a situation where they would have been under that pressure. It’s finding a way to justify their actions without judging them. But also to make sure I was protecting the real Sadie; I felt like she’s already suffered so much.  

Deceit is on Friday 13 August, 9pm. Channel 4

Images: Channel 4