'I think it is better than the first one': Smethwick-born Dame Julie Walters talks ahead of Mamma Mia: Here We Go Again release

That was until she saw the script and all her concerns were banished in an instant.

It has been ten years since Mamma Mia! broke a slew of box office records, and Walters says she feared a follow up would be ‘awful’.

“I couldn’t see how it could work and what they could do with us,” she said.

“My first reaction when my agent told me they were making Mamma Mia 2 was, ‘oh God no, it is going to be awful’.

“But the script was so good. I think it is fantastic. I think it is better than the first one," said the Smethwick-born actress.

Mamma Mia! Here We Go Again – released in cinemas across the Black Country and Staffordshire today – features Walters reprising her role as Rosie, alongside other returning stars Pierce Brosnan, Christine Baranski, Amanda Seyfried and Colin Firth.

And there’s an added sprinkle of stardust with the appearance of Cher.

As Brosnan explains, during filming he had a day off so decided to take his mum out to lunch.

But as fate would have it, his phone rang to call him to set. “I said to her, ‘Well, mum, you may as well come with me, we’ll go to work’ and we went down to the studio’. I had no idea why I was being called in, just to be part of the ensemble, I guessed.

“And there was Cher. Everyone was there with their mothers and fathers and boyfriends and girlfriends – all watching her do her thing.”

Cher plays Ruby, the mother of Meryl Streep’s character Donna Sheridan.

“My mum sat there with Meryl and Christine and Julie and she was in heaven,” Brosnan, now 65, remembers. “It was a glorious day, a fabulous day. It was five takes with 300 people there, seven cameras.

“I filmed it too that day. I’ve got it on my camera, tucked away.

“It was a little bit surreal, but the air crackled with anticipation for her arrival, that’s for sure. And she was so gracious with us all; she knew she was coming into a company of actors and she’s a great actress herself.”

Baranski, who returns as Tanya, laughs at the memory. “We were all watching, because she really is a rock chick. She’s the real deal. Meryl turned to me at one point and said, ‘So this is how it’s really done’.

“But if anything she was rather shy about it and intimidated.”

Baranski plays Tanya in the movie – the other half of the double act to Walters’ Rosie. Both characters were introduced as Donna’s (Meryl Streep) best friends and the other two-thirds of the Dynamos in the first movie a decade ago.

And Baranski revealed that Walters broke down in tears during filming when she returned to the set after being made a Dame Commander by the Queen. “She was in the middle of filming Angel Eyes and then she got her Damehood and came back on the set,” Baranski said.

“Amanda [Seyfried] and Julie and I were doing the cake-eating sequence and everybody started gathering around and we started thinking, ‘What? Is everybody gathering around to watch the filming of the rest of the song?’ “But no, suddenly they started playing the music from South Pacific, There’s Is Nothin’ Like a Dame, and we all sang to Julie and she was just in tears.”

“It was a great moment, because she’s just a great lady. A great actress and a great person.”

Attempting to follow up such a classic is no easy task – even for the biggest stars. It is still hard to comprehend the success of that first Mamma Mia film in the UK, where it made almost £70 million. When it was released in 2008, during the depths of the credit crunch, it became the highest grossing film of all time at the British box office.

While it has since been usurped by a number of big-budget blockbusters which have pushed it down the rankings, it is still the most successful musical.

For the follow up, the pressure was immense, and Cher herself admits she was petrified on her first day on set. “I was terrified!” the 72-year-old confesses. “Everyone had been together and my character wasn’t very liked so I was nervous, but everyone was nice to me.

“Meryl was behind a piece of scenery watching me do my number and that made me feel good after the fact but it was hard to go on a set where you were a stranger to everyone. I knew some of the people, but I am doing this ‘mean grandmother’ thing. In the end, I felt really loved and like a great grandmother.”

Mamma Mia! Here We Go Again is released in cinemas today.

l See a full review of Mamma Mia! Inside The Ticket.