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'Deceit' star Niamh Algar: 'The lines of what is real and what is not begin to blur...'

Niamh Algar in character as 'Sadie Byrne' in C4's Deceit, sitting at a bar and wearing glittery make-up as part of a previous undercover sting
Niamh Algar as 'Sadie Byrne' in Deceit (Image credit: Channel 4)

In July 1992, Rachel Nickell was murdered while walking with her two-year-old son, Alexander, on London's Wimbledon Common. As the police searched for Rachel's killer, an appeal on Crimewatch led to several viewers naming Colin Stagg, who often walked his dog on the Common, as a suspect. 

Lacking forensic evidence to link Colin Stagg to the crime, the Metropolitan Police took a different approach, devising Operation Edzell, in which a female undercover officer would build an intimate relationship with Colin Stagg and gain his trust, hoping for him to either confess to the killing or to eliminate himself from the inquiry.

C4's new four-part drama Deceit explores this operation as undercover officer 'Sadie' (played by The Virtues star Niamh Algar) — whose real name remains classified — poses as 'Lizzie James' and makes contact with Colin Stagg, and the series reveals the controversial honeytrap operation at the heart of the investigation. It led to the police wrongly arresting innocent Colin Stagg.

We spoke to Niamh to find out more...

Niamh Algar on her introduction to the role of Sadie

"DC Sadie Byrne works at the Metropolitan Police, and she's a covert officer who has been enrolled to play 'Lizzie James' on Operation Edzell.

"The way it started was just having a conversation with Emilia [di Girolamo], our writer, and Emilia's main concern was to maintain the anonymity of the real Sadie Byrne, so for me not to go too far down the rabbit hole of trying to make any of her characteristics too close to who she is."

Sadie (Niamh Algar) leans up against a bookcase full of criminal profiling textbooks

Sadie (Niamh Algar) is recruited to build an intimate relationship with suspect Colin Stagg. (Image credit: Channel 4)

"So I met and talked to female officers who would have been working at the time, but not on this case, and just asked them how they went about their lives, and how the way they were treated affected them — what it was they were willing to do to carry out certain ops. So instead of trying to focus on Sadie Byrne, it was trying to get a full recognition of women in the force at that time."

We see early on in the series that Sadie doesn't get recognition for the important and dangerous work she does on a previous case. How does that affect her?

"Yeah, there's numerous things that are driving Sadie during the story, one of them being the fact that she doesn't want anything like this to happen again, she wants to find Rachel's killer. But we're also in a time where women weren't exactly moving up through the ranks, the idea of a woman being promoted was incredibly rare — so the fact that she was chosen to be the centre of such a massive case was a huge thing for a woman in the force at that time. Her doing this, and getting this right, would pave a way for women in her situation."

Baz (Nathaniel Martello-White) and Sadie (Niamh Algar) sit in a pub together, drinking and playing with a deck of cards

Colleague Baz (Nathaniel Martello-White) helps Sadie (Niamh Algar) to prepare her backstory before going undercover as 'Lizzie'. (Image credit: Channel 4)

You were effectively playing two characters: Sadie, and 'Lizzie'. What was that like?

"In my trailer, I had one side that was kind of like 'Lizzie Land', and all the characteristics and likes and dislikes of this character, and then there was 'Sadie's World' on the other. Going from one costume to the next in the same day was nice to lean into, as a story — you could understand how somebody could get so lost, and where the lines of what is real and what is not begin to blur. Sadie is trying to lead with her gut, trying to instinctively read the situation, but if you live so long in the headspace of another person, you could understand how you could lose sight of what you feel is right and what's wrong."

  • Deceit launches on Friday August 13 on C4 at 9pm. The full series will be available as a box set on All4 after episode one airs.