Dominic Cooper insists it was ''lovely'' working with his ex-girlfriend Amanda Seyfried on 'Mamma Mia! Here We Go Again'.

The 40-year-old actor and Amanda, 32, first met on the set of the 2008 musical movie 'Mamma Mia!' and started dating but their on/off romance ultimately came to an end until 2010.

The pair were reunited for the new film playing married couple Sky and Sophie and Dominic insists it was wonderful to get to work with Amanda again, because they had remained friends despite their break-up.

In an interview with UK TV show 'Lorraine', he said: ''It was lovely. We stayed in contact. We've worked together so much in the past. With everyone in that cast, getting back together after that amount of time, the only way I could really think of what it must be like is like a school reunion.''

Amanda is now married to Thomas Sadoski, with whom she has a 16-month-old daughter, whilst Dominic split up from his long-term partner Ruth Negga in April.

Dominic stars in the film - which is soundtracked by the music of ABBA - with an all-star cast which includes Lily James, Julie Walters, Meryl Streep and Pierce Brosnan among others.

Screen and stage icon Cher is a newcomer to the franchise, playing Ruby Sheridan, Donna's mother and Sophie's grandmother, and Dominic admits it was a ''surreal'' experience to get to work with her.

He said: ''It was just, I don't know, so many parts of it were so surreal. Seeing her approach the set ... she was quite frightened as well in terms of going in to act on a show where the cast all knew each other very well. ''Everyone was very welcoming. We all got on tremendously well. There was a moment when all the lights went down on the set - everyone was there that day as it was towards the end where we all get back into our purple Lycra. She walked up onto this platform, she'd chosen her own costume - she'd brought with her own wonderful hot pants with sequins in them - and all the lights went out and this spotlight came on her and she started to sing 'Super Trouper' and it was one of the most mesmerising moments I've ever been part of on a film set. You could feel the atmosphere vibrating. Seeing a woman doing what she does best so wonderfully, I think it was just genius she was part of it.''