Line of Duty's Vicky McClure and Morven Christie to star in new BBC1 thriller The Replacement

The three-part series written by Joe Ahearne is the story of Ellen (Christie) – a woman who becomes unexpectedly pregnant and hires Paula (McClure) to fill the gap while she’s on maternity cover.

However, Ellen soon starts to view Paula as a rival in the office with her replacement muscling in on her boss and friends. But she’s the only one who sees it, and soon even her own husband is doubting her state of mind.

Actress Vicky McClure is best-known for playing the role of DC Kate Fleming in Line of Duty, while Christie is currently starring as Amanda in ITV's Grantchester. Last year she also played Alison in BBC1 drama The A Word.

Vicky McClure in Line of Duty alongside Martin Compton and Adrian Dunbar

“I like stories about paranoia where our main character is the only one who can see what's going on while everyone around them thinks they're going crazy,” said Ahearne.

“Someone going on maternity leave and having to deal with a temporary replacement seemed like a great way to explore this emotion. She watches what's going on around her and sees evidence everywhere she looks that she's being undermined.

“Most of us have the secret fear that we're not good enough and feel envy when we see others navigating professional and social situations more suavely than we think we can manage.

“The Replacement turns that up to 11," the writer added. "The fact it's a pregnant woman going through this intensifies the dilemma.

"Women get attacked from every side when they make decisions about how to manage the change in their life. Whatever decision they make is challenged and dissected. It's the perfect landscape for paranoia and suspense.”