Now here’s a sight you don’t see every day – Julie Walters singing ABBA’s Chiquitita to Mery Streep. But don’t worry, it’s only for the film version of the huge stage hit Mamma Mia!

ABBA: the Mamma Mia! Story tries its hardest not to be an extended plug for the movie, which has its premiere this week, and it almost succeeds: we hear the story of the ebullient stage musical, which began in London then went on to conquer the world; and ABBA’s driving forces, Björn Ulvaeus and Benny Andersson are interviewed at length.

But this is really all about the film. The programme has secured lots of behind-the-scenes footage, and interviews with its stars, a very jolly Meryl Streep (who has, incidentally, a hell of a singing voice – just listen to her belt out The Winner Takes It All), the suave Pierce Brosnan,and a wry Colin Firth (yes, he sings!), who has the grace to look sheepish as he tells us: "Very few straight males of my generation would put their hands up and admit to being an ABBA fan."