Ten years after the first movie, Mamma Mia 2 has roared into cinemas – bringing with it a whole host of ABBA songs and familiar faces.

Alongside Christine Baranski, Julie Walters, Pierce Brosnan, Stellan Skarsgard, Colin Firth and Meryl Streep, Amanda Seyfried and Dominic Cooper have reprised their roles as the (now married) couple at the centre of the plot, Sky and Sophie.

However, it was an admittedly surreal experience for the actors as, while filming the original movie, Seyfried and Cooper started dating in real life, only to call time on their relationship three years later.

Since then, Seyfriend has welcomed her first child with her husband, Thomas Sadoski – and, in a revealing new interview with The Mirror, admitted that Sadoski was a little jealous when she began working with Cooper again.

“I think [Sadoski] has the same kind of issues that I would have if we were hanging out with his ex-girlfriend from long ago. I think it’s always like, ‘I’m so in love with this person, so that person must be so in love with her too’,” she said.

“I’d guess he assumed Dominic is in love with me the way he’s in love with me. And it’s just not the case.”

Eventually, though, Cooper and Sadoski got along great.

“It’s sweet,” Seyfried continued. “I’d rather he be jealous than completely fine with it. He’s been great. He’s very supportive and he loves this movie, and he and Dominic got along absolutely fine when we were shooting.”

Of Cooper, she added: “We split about three years after the movie came out and after we split we became really close friends. The last time I’d seen him was when I hung out with him on my 30th birthday. So it wasn’t weird seeing him again.”

Read more: Amanda Seyfried nails the big difference between being a girl and a woman

Cooper, who reportedly split from his girlfriend of eight years Ruth Negga in April 2018, echoed Seyfried’s sentiments in an interview with Attitude.

“She’s a friend,” he said of his co-star. “It was always going to be OK. You just have to be delicate with those situations. She’s married now and has a beautiful child.

“We knew we were going to be working together [again] on a set, going back to a part which was certainly going to remind us of 10 years earlier, but I know her family, I know her mum, who was there a lot. It was a pleasant atmosphere. It was really interesting to see how different our lives are after 10 years. It is a long time and it was nice to spend time [with her].”

Unless they’ve done something unspeakably awful, it’s not unusual to want to stay friends with an ex. In fact, if you ended on reasonably amicable terms – and particularly if you move in the same social circles – attempting to maintain a friendship often seems like the most sensible, mature option.

However, a recent study suggests that you should only try and stay friends with your ex if you’re certain you don’t still harbour feelings for them – or it could have serious repercussions on your future relationships.

Lindsey Rodriguez, assistant professor of psychology at the University of South Florida and lead researcher on the study, explains: “Generally, this research shows that communication with former partners is not universally good or bad for current relationships. The important factor is why the person continues to communicate with the former partner.

“It is possible to continue to stay friends with an ex for purely platonic reasons, and that can be inconsequential or positive for the current relationship.”

However, she adds that maintaining contact with an ex can make it difficult to truly move on. “Many people find themselves ‘stuck’ on former partners or unable to really break away from the idea of a relationship with them,” she says.

“When this happens, they experience higher rates of depression and anxiety, and are less likely to find themselves in a healthy new relationship.”

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