A whodunnit within a whodunnit, new film See How They Run is set around a fictional West End production of Agatha Christie’s The Mousetrap.

And it’s not just the play which audiences will recognise – a cast of famous faces make up the list of suspects, with Sam Rockwell and Saoirse Ronan playing the police team sent to crack the case.

Rockwell, who won an Oscar for his portrayal of a troubled police officer in Three Billboards Outside Ebbing Missouri, told Sky News this latest role – a cynical Scotland Yard detective – was an opportunity for him.

“I am attracted to kind of misanthrope characters. And I hadn’t done a British accent in a while – I’d never done it in front of a camera, I’d done it on stage twice, so that was really intimidating, but fun and challenging.

“But again, to play a grumpy detective is fun, aside from the British accent.”

The 53-year-old actor admits bingeing on classic movies in order to nail the right voice for the character.

“I watched everything – you name it, I watched it. Anything I could get my hands on from Nil By Mouth to Mike Leigh to Educating Rita, to Alfie.”

The rest of the ensemble cast is a mix of Hollywood stars and British comedy actors. Rockwell says that having so much talent on set helped him to perform at his best.

“It makes a big difference when you get Harris [Dickinson] or Pearl [Chanda] or David Oyelowo or Ruth Wilson or Adrien Brody, Reece [Shearsmith], you know, yeah it makes a big, big difference.

“It just brings out the best in you because they’re out there bringing their A-game… It’s inspirational.”

That mix of British comedy stars and A-listers was helmed by director Tom George, who is known for his Bafta-winning mockumentary This Country.

George told Sky News he made a conscious decision to do something different with See How They Run – though there are similarities between both projects.

He explained: “When you’ve done a thing everyone wants you to do the thing again, generally, I certainly got sent a couple of scripts for mockumentaries and it’s like, that’s the last thing I want!

“So, this came along just at the time when we were finishing the final series of This Country, and on first glance they couldn’t be more different, but it was also the sort of common threads between them that made me feel like it was something that I could do justice to.

“You know, although it’s a whodunnit and it’s a period setting, at its heart it’s a character comedy and it’s the story of these two detectives and whether they can kind of come together and crack this case.

“And you’ve also got this meta layer in play – just as in This Country you’ve got the mockumentary form and you can use that to tell a story in interesting ways or to add humour in a certain way.

“It’s a whodunnit, but it’s also a film that’s about whodunnits, so again, you’ve got this sort of extra layer to sort of hopefully tell a story in a sort of slightly original way.”

With the movie set around the West End, the pandemic presented the film-makers with an opportunity to shoot in theatres shut due to COVID that would, under usual circumstances, be impossible to use as locations.

“It was semi lockdown and we went to the Old Vic and then we shot at the Savoy Hotel,” Rockwell explained.

“I shot there about nine months ago for another film and it was totally different, people everywhere. So really the contrast was spooky and stunning.”

Rockwell, who has spent much of his career on stage, added it was hard not knowing what the future held for that industry.

“We were worried about theatre. It’s come back, thank God – I was in rehearsals for a play right before the pandemic and then we recently just did it on Broadway. But it was scary, people saying theatre might be dead permanently.”

George admits while it was a great opportunity in terms of making the film, it did feel strange.

“It was bittersweet because, you know, these amazing venues were closed down, couldn’t have people in and didn’t know when they were going to be able to come back.

“A little silver lining was we were able to hopefully help them bridge the gap a little bit in a business sense, but also had the opportunity to film in these just incredible spaces that I’m not sure when you’d get the opportunity again.”

See How They Run is in cinemas now.