Lily James is keen to play "unlikely roles".

The 36-year-old actress - who stars alongside Riz Ahmed and Sam Worthington in the thriller film Relay - has revealed that she's eager to challenge herself in her professional life.

Asked if she would've been interested in Relay if it was more "conventional", Lily told The Hollywood Reporter: "Honestly, I was so excited to work with [director] David Mackenzie and Riz that I almost would've done any old thing that they put in front of me.

"That being said, you love to find work that's surprising and characters that take you in a direction you didn't anticipate. And particularly at this point in my career, I want to keep pushing myself to play unlikely roles, roles that surprise me, and have something to get my teeth into. So that [unconventionality] was definitely what was very appealing about this role and story."

Lily recalled being wowed by the Relay script, and she hopes that film fans are similarly surprised by the plot.

The actress explained: "Relay felt like this really gripping, dark thriller that exposes the world of whistleblowers and the idea of this greater control and always being watched. It felt really surprising, and I was thrilled to get to work with such a unique filmmaker in David Mackenzie. His movies feel so cinematic and grounded and bold and original."

Lily also relished the experience of working with Riz, describing her 42-year-old co-star as "one of the most exciting actors out there".

Lily and Riz managed to develop a great chemistry, even though they rarely filmed together.

She said: "Riz is also one of the most exciting actors out there, especially when you see what he's able to convey with no dialogue in the first 20 minutes of the movie.

"The connection we were able to build despite our characters very rarely being in the same room together was a real challenge. And when I watched the movie for the first time at TIFF on the big screen, I was like, 'Wow, it's incredible that there's this great electricity between these two characters when they barely meet.' So it was quite a sleight of hand that David pulled that off in terms of filmmaking."

Meanwhile, Lily previously admitted that she still suffers self-doubts.

The actress told The Talks: "I don't stay up all night getting nervous about work. I do get frightened of not being good enough.

"I'll get quite anxious after days where I've had a big emotional scene, I worry that I haven't given enough or I get frightened that I haven't been true enough. So that's a kind of fear that lasts pretty much the whole shoot. But it's doesn't make me nervous, weirdly -- except in auditions."