Fans of silver jump suits and seventies music unite. A new musical called Mamma Mia!, based on 28 catchy Abba tunes by the group's Benny Andersson and Bjorn Ulvaeus, opened in London's West End on Tuesday night.

More to Abba than pop?

Two and a half million pounds have been taken in advance bookings

The first night of the show came exactly 25 years after Waterloo won the Eurovision Song Contest, and now there are those who say the quartet from Sweden should be reassessed as true musical greats.

Music producer Pete Waterman - the man behind current chart act Steps - says: "If you look very deeply into the Abba sound, it's actually very classical. It's very mid European - Brahms and Beethoven - more classical probably than any other pop music has been."

One of the band members, Bjorn Ulvaeus, says very modestly: "We just composed music we liked. There was no formula. We just tried out everything that we had consumed as perceptive youngsters growing up and listening to everything.

"All that came out, but in our version later on. There was no formula, if you listen to the songs you will hear there is no formula."

Watch Rosie Millard's report

Abba may have been very musical, but the trouble is they were also just a bit naff and surely this comeback must be due to a joke somewhere. Not at all, say the hard core fans.

Kathryn Courtney O'Neill, President of the Abba UK Fan Club, says: "I don't think Abba were ever naff, they just weren't that popular during the eighties."

Not the real Swedish foursome

Anyone who was hoping the new musical would feature lookalikes of the famous four on stage would have been sadly disappointed.

Rehearsing one of those catchy numbers

Bjorn Ulvaeus does not want to see those outfits again: "I just don't want it to be misunderstood by people. I don't want them to come in and think that they will hear Abba. It is a musical that they are about to see and I don't want to see disappointment."

Instead the musical is about a young woman and her mother who reflect on the past and look to the future on the eve of the daughter's wedding day - all accompanied by tracks from Abba's back catalogue.

Mamma Mia! has already taken two and a half million pounds in advance bookings, and seems poised to be one of the West End's musical hits of the year.