London, April 7 (Reuters): Nothing — not even $2 billion — could tempt Abba back together again. After 30 years, the Swedish supergroup might even have trouble remembering the words of their pop classics.

And the sight of their outrageous stage outfits is enough to make 58-year-old Bjorn Ulvaeus cringe nowadays.

Thirty years to the day after Abba won the Eurovision song contest with the instantly catchy Waterloo, the bearded songwriter is fiercely proud of their music — but they will never strut their stuff again.

Four years ago, Abba were offered $1 billion to re-form. The answer was “No”. But what if that figure doubled?

“No, not even if you did that,” Ulvaeus said.

“It is never going to happen again. I think it is a bit too long now. We split up in 1981. People haven’t seen us as a group since then and it would come as such a disappointment to them.”

As for the spangly jumpsuits, Ulvaeus said: “I haven’t squeezed into them for years. I still had a couple of them in the wardrobe and would get into them on a Saturday evening — but not any more. They are in a museum now.”

Tuesday marked another Abba milestone — the musical, Mamma Mia, which is based on their hit songs, celebrated five years playing to packed houses in London.

Abba songs may be staple fare in karaoke bars around the world but songwriter Ulvaeus would need prompting.

“I cannot remember a whole lyric of any that I have written,” he confessed. “I am translating them into Swedish now for the first time because we are doing a production in Sweden at the beginning of next year. I find that I don’t know them by heart — not one of them.”

Abba once ranked alongside Volvo as Sweden’s most famous export. The Mamma Mia show could prove even more profitable than the 350 million Abba albums sold around the world.

“It’s possible,” Ulvaeus said. “Mamma Mia is going to run for a longer time than Abba did. So who knows? We will see.”

The show certainly generates Money, Money, Money. With 11 productions currently running and six more in the pipeline, it has grossed over $750 million worldwide and has been seen by more than 10 million people. In box office takings, it should effortlessly exceed the billion-dollar mark set by Phantom of The Opera.

The musical weaves in Abba’s back catalogue to tell the story of a single mother living on a Greek island with her daughter, who is getting married. Reading her mother’s diary, she finds that any one of her mother’s three lovers could be her father. All get invited to the wedding.

Ulvaeus reckoned the timing was perfect. “I think the world perhaps was ready for something happy, a comedy. The big musicals in the eighties and the beginning of the nineties were rather sombre — like Phantom of the Opera and Les Miserables — wonderful musicals but of a different kind.”

And Ulvaeus still shakes his head in wonderment. “I am fiercely proud, amazed and astonished. I thought this would be a little show running for perhaps a year in a small theatre in London.”