Shortly after giving birth Carey Mulligan arrived on a movie set. It was a role she couldn't turn down.

If I won the lottery, I would buy a private island and invite Stevie Nicks and Lindsey Buckingham from 'Fleetwood Mac' to perform for me. Just me.

I would force them to stare deep into the other's eyes and recreate their iconic 1997 Silver Springs performance, where Nicks all but cast a spell on her petrified ex as she hauntingly chanted "you'll never get away from the sound of the woman that loves you".

Luckily for Stevie and Lindsey, I haven't won the lottery. Unluckily for folk-duo McGwyer Mortimer, a man named Charles Heath has. And he had my idea first.

If you haven't heard of McGwyer Mortimer, that would make perfect sense. After all, they are a fictional band concocted by writers Tim Key and Tom Basden for their new film, The Ballad of Wallis Island, starring Carey Mulligan.

Ahead of the film's release, I sat down with Carey and Tim to chat about the project. What began as a short film back in 2007, called The One and Only Herb McGwyer Plays Wallis Island, has now been massaged into a feature-length comedy-drama, directed by James Griffiths.

The film follows eccentric super-fan Charles (Tim Key) who, after winning the lottery, contracts his favourite musician, Herb McGwyer (Tom Basden), to perform a private gig on the remote Wallis Island.

"We really loved making the short film, we felt like we were making something that was good, that we enjoyed. We were really proud of it," Tim told Mamamia.

Watch: The Ballad of Wallis Island - Official Trailer. Post continues after video.

That was 18 years ago. At first, it felt too precious to re-visit. But the writers couldn't help but think there was more of Wallis Island to explore. 

"More than any other project, there was a nostalgia element of thinking it would be amazing to go back to Wales and do exactly the same, basically, but everything slightly bigger. And slightly better, hopefully," said Tim.

The comedian knew, however, that there was one thing missing. Or, rather, one person.

"We always needed to expand [the film] in terms of people," said Tim. "I think people would get pretty frustrated with those characters after a while, well… with my character, Charles."

Enter: Nell Mortimer (played by Carey Mulligan). In the feature film, Nell is the second half of disbanded folk-duo McGwyer Mortimer, alongside Herb.

In true 'Fleetwood Mac' fashion, the musicians dated before breaking up romantically, and eventually professionally. Behind Herb's back, Charles invites Nell (and her new husband) to the island to reunite his favourite band. 

From the get-go, Tim knew exactly who he wanted to play Nell. And he wasted no time emailing Oscar-nominated actress Carey Mulligan with the subject line "Film Opportunity".

Before the actress had even read the script, her husband Marcus Mumford — the lead singer of folk rock band 'Mumford & Sons' — encouraged Carey to join the project, as he was a big fan of the creators.

Carey, however, didn't need much convincing to get on board, saying it was all "gut instinct".

Carey Mulligan and Tom Basden play Nell and Herb in the film, who were once in a folk duo called McGwyer Mortimer. Image: Focus Features

"It's not every day that you read such a good script," Carey told Mamamia. "I was really blown away by how brilliant it was. The world is so appealing and the story is great."

Just like that, the "final piece in the jigsaw" had signed the dotted line and Tim was over the moon.

"We were fortunate enough to get our first choice. I mean, I can barely look at her," he gushed over his co-star. "Carey did exactly what we wanted for the film, times about a thousand. She elevated it."

While immersing herself in the character of Nell, Carey had not long welcomed her third baby. And the newborn quickly became a permanent fixture on set. 

"It was very sweet, she was just around," Carey said. "She was upstairs while we were filming. A little baby mascot on set makes everyone happy. It was a very happy set, so it's kind of a perfect place to have a tiny baby."

The filming location also held a personal significance to Carey.

"It was shot where my mum's side of my family is from in Wales. So, we were around places that I went to when I was little and had lots of extended family. I got to introduce [my baby] to my great aunt."

As she balanced the acting gig and motherhood, Carey explained that "the boys were very accommodating to [her] reluctance to leave the house", and even recorded some of the music for the film in her husband Marcus' studio.

"It was amazing. I just loved all the music from the first time [Tom Basden] sent it to me. He just put so much story into all of those songs; a lot of thinking about what [Herb and Nell's] relationship had been was baked into all the music. It was lovely."

Carey Mulligan and Marcus Mumford wed in April 2012. Image: Getty

Music, and the way it holds memories, is at the heart of this film.

For Carey and Tim, there are moments in their own lives that are defined by soundtracks.

"When I was 18, I moved to London. I was doing a play and I discovered Joni Mitchell, quite late," Carey told Mamamia.

"I was like, 'Oh my god, have you guys heard of this artist?' I listened to 'Blue' on repeat for about six months. So I always think of my little room in Highgate when I hear that song."

Similarly, an 18-year-old Tim found himself listening to nothing but 'The Beatles' while he lived in Eastern Europe.

"In the flat there was a record player and one album, A Hard Day's Night by 'The Beatles'. I just had that constantly on repeat. I couldn't understand the television, there was no radio, and I refused to have silence. I would just spin it over and then do it again and then turn it back over. Whenever I hear anything from that album, it takes me back into that time of my life, to that pokey little flat and that city."

It makes sense, then, that Tim would invite 'The Beatles' to his own private island if given the opportunity. But what about Carey?

"I don't know who I want to be in the kitchen with. I think I would be weird around a lot of people," Carey said.

"Don't worry, I think I'm going to be quite weird with Ringo, to be fair," joked Tim.

After some deliberation, Carey settled on the 'Backstreet Boys'.

"I don't know if I would just hide in the toilet if they were actually in my house. But I'll take them anyway," she said.

The Ballad of Wallis Island was written by Tom Basden and Tim Key. Image: Focus Features

Fan culture is, of course, a big topic of the moment. Just look at all of the parasocial Swifties (guilty) after her engagement to Travis Kelce.

In The Ballad of Wallis Island, the character of Charles has a similar devotion to McGwyer Mortimer. For Carey's part, she has "definitely written to people" she admires in a fan capacity.

"I've gotten hold of email addresses and sent gushing emails to people to say 'You're amazing'. But I haven't physically approached them or tried to go to their house, which I think is a good boundary for me," the actress laughed.

"I remember writing to Daniel Kaluua about a movie once and telling him how brilliant he was. I wrote to Amy Adams after Arrival. Never met Amy Adams, I was just like, 'I've got to tell you, you're amazing'. It was the year that she did Arrival and Nocturnal Animals and I wrote to her being like, 'You're the best.'"

There is also a poignant moment in the film where Nell leaves behind a keepsake for her biggest fan, Charles. It's a souvenir that parallels one in Carey's own life.

Tim Key, Carey Mulligan, and Tom Basden at the Gala Screening of The Ballad Of Wallis Island. Image: Getty

While filming Maestro, a 2023 biographical drama about American composer Leonard Bernstein and his wife Felicia Montealegre, Carey received a token she will cherish forever.

"When I did Maestro, the Bernstein children gave me their mother's lighter, who I was playing in the film. It was her lighter engraved with her name," said Carey, who earned an Oscar nomination for her performance in the film.

"They gave that to me at the beginning of filming and I used it all the way through the film. They gifted it to me. I still have it. That was super meaningful."

In total, there are only five characters that appear in The Ballad of Wallis Island. The crew was similarly intimate, with no more than 50 people working together in coastal Wales.

"I love very small casts. I love when there's very few people and you're all getting to work intensely with each other every day," Carey told us.

Tim agreed, adding: "It was really an enjoyable place to go to work."

"I remember shooting scenes where you feel like everyone in the room is leaning forward and is into it, or is even laughing if it's a funny scene. And then as you leave the room there are people nodding, sort of going 'Yeah, this is quite good'. That means a lot," he added.

"You'd be mad to rely on people coming up to you and saying, 'Honestly, this is hilarious'. But just a glint in a boom operator's eye where you think, 'Oh, he's into it', does mean a lot."

THE BALLAD OF WALLIS ISLAND is in cinemas August 28, 2025.

Feature Image: Getty