Carey Mulligan on returning to folk music for Ballad of Wallis Island

The film was written by comedians Tim Key and Tom Basden – who also star – and directed by James Griffiths, and Mulligan has explained that stepping back into the world of folk music was just one thing that made the project an enticing one.

"I'm not looking for a singing part, gonna put that out there!" she told RadioTimes.com during an exclusive interview. "But I just loved the script so much.

"It's a very romantic world, the music – and there's just so much about music that is so evocative and it brings us to points in our lives so instantly.

"Like a smell, you just say one song, and immediately you go back to being 21 remembering exactly where you were when you heard it.

"And the script is so full of that. So it's definitely so interesting to explore as a subject. But no, I wasn't hankering after a solo on this one!"

The film started life as a short which Key, Basden and Griffiths had made all the way back in 2007 – and the idea of expanding it into a feature was something that regularly came up in conversation whenever the trio met up.

"We definitely all thought about it," explained Griffiths. "We went for a lot of curries, and would end up saying, 'Yeah, we got to go back to that thing.'"

He added: "I think we just all felt very nostalgic about how much fun it was to make the short, and as you increasingly move away from that period, you realise how rare that is, that you come together, enjoy each other creatively that much.

"So, yeah, it was something that we always discussed, and it became, towards the end, kind of untenable, like, just painful that we would never [do it]."

"He moved back from LA, just expressly to kind of put pressure on us!" interjected Basden.

When it came to eventually sitting down to write the script, Basden explained that the idea for how best to expand the short came together rather quickly.

"We had a real breakthrough moment where we came up with the character of Nell," he said.

"And through her just introduced this idea of the backstory, of history, the sense of nostalgia and loss and melancholy that comes with characters looking back at a point in their life – which all of them are in some way doing.

"So I think that was the moment when the film started to to crystallise for us and feel like this could be a lot bigger and better than the short film."

As for the central character of Charles – as played by Key – the comedian explained that he didn't change too much from the original short beyond being given a more in-depth backstory.

"Really, it was just the same as doing the short, you're just doing it for longer," he laughed.

But he added: "I do think that of all the different parts that you do along the way, this is one of my favourites. I don't know why. It feels very... it's terrible [but] it feels natural to do it. I mean, the guy's all over the place, but, yeah, I like doing it!

"[And] with any part, once you feel like you know you're under the skin of that part, then it's kind of interesting seeing him in different situations. And [there's] something quite satisfying about knowing instinctively what this person would say in this situation, even if that's nonsense."

The Ballad of Wallis Island is released in UK cinemas on Friday 30th May.

Check out more of our Film coverage or visit our TV Guide and Streaming Guide to find out what's on. For more from the biggest stars in TV, listen to The Radio Times Podcast.