Four years ago, Abba were offered $1bn - that's right, a billion - by an Anglo-American consortium to re-form. The Swedish quartet, who burst on to the scene 30 years ago next Monday, when they won the Eurovision Song Contest in Brighton with "Waterloo", didn't take long to dismiss the offer out of hand. "I didn't fancy the idea of re-forming at all," says Bjorn Ulvaeus, one of the Bs of pop's most famous acronym, as he settles on a sofa in a discreetly luxurious hotel in Covent Garden. "Honestly, it would have put 10 years on my life. Normally we don't even discuss these offers, but this time we did. You would have to be dead not to be dazzled by that much money. But everyone came to the same conclusion. We would have had such a terrible time."
Ulvaeus is the bearded one with the wry grin and questionable taste in spangly jumpsuits - though I know that doesn't narrow it down much. He continues: "Can you imagine hearing 40,000 people on the other side of the curtain, really expecting something special, before the show? They remember us as energetic and joyful, but the curtain would pull back to reveal four geriatrics on stage. It would be such a shock for the audience.
"We would never re-form. It would spoil the purity of what we did in the first place. Anyway, bands usually re-form because one or two members need the money..." A man who has been described as more English than the English, Ulvaeus tactfully leaves the rest of the sentence unspoken.
So we can't look forward to appearances by Abba on youth-orientated TV shows? "Would becoming an ageing rock-star appeal?" Ulvaeus asks. "No, never, no way. What a nightmare it would be to appear on Top of the Pops beside all those youngsters."
But fans who will never experience the exquisite pleasure of seeing the original foursome perform on stage again can at least console themselves with an Abba musical that redefines the hoary old critical chestnut of "a rattling good night out". Mamma Mia! is the one pop musical you don't have to be embarrassed about telling your friends you've seen.
There's certainly an electric atmosphere the night we attend. A white stretch limo pulls up outside the Prince Edward Theatre in London. It disgorges eight riotous hen-party girls swigging from champagne bottles and wearing more glitter than a glam-rock band.
These women are typical of the usual exuberant Mamma Mia! audience. Whether they are eight or 80, or from Tokyo or Towcester, they've all come to party. From the moment of the pre-show announcement - "We'd like to warn people of a nervous disposition that platform boots and white Lycra feature in this production" - the whoopin' and hollerin' resembles a Southern Baptist church service.
By the time of the encore, when the cast appear on stage in the aforementioned platforms and Lycra for the inevitable "Dancing Queen", the question from the stage - "Do you want more?" - is unnecessary. Of course we do. Mamma Mia! passes the acid test of any memorable musical: you find yourself still singing the tunes the following day - if not the following week.
The premise of Mamma Mia! is pleasingly simple. Abba hits are worked into a straightforward plot about a young woman called Sophie. She is about to get married on the idyllic Greek island where she and her fiercely independent mother Donna run a bar. Unbeknown to her mother, Sophie has invited to the wedding the three men who could be her father.
The show is as camp as Christmas, and the key to its appeal lies in the fact that it does not take itself the least bit seriously. Unlike some more po-faced West End musicals - you know who you are - Mamma Mia! very much has a smile on its face.
And so do its producers. The show, which celebrates its fifth anniversary this week, has racked up more than $750m (£410m) across the globe. It is now playing in 11 locations - the latest production is in Seoul, South Korea - and another six are in the pipeline. The show has been seen by more than 10 million people. You can see what Ulvaeus means about not needing to make a financially motivated comeback.
Ulvaeus, who divides his time between Sweden and a house in the Chilterns, reveals in his impeccable English that Mamma Mia! "is going to make me richer than Abba ever did". As co-producer and songwriter, he's coining it: Money Money Money, indeed. Merchandise is flying out of the stall in the theatre's foyer. If you loved the show, what would you like as a souvenir? That's right; a pair of Mamma Mia! flip-flops.
I talk to Judy Craymer, the show's producer. "I remember when I thought it would be great to be able to afford a taxi," she laughs. "Now I can afford to keep a taxi waiting."
The show was Craymer's brainchild. Once Tim Rice's assistant, she first met Ulvaeus and his songwriting partner and former Abba colleague Benny Andersson more than 20 years ago. At the time, she was executive producer of the musical Chess, which Ulvaeus and Andersson co-wrote with Rice. "As a teenager, I was much more into rock and punk," she remembers. "But when I met Bjorn and Benny, I was bowled over - 'Wow, I've met the men who wrote 'Dancing Queen'!"
She had been trying to convince the Abba boys to let her create a musical based on their songs since 1987. She felt the tracks had an innate theatricality that would translate effortlessly into a musical. "Bono says that Abba wrote great songs for women, and that's absolutely right. Remember that line in 'The Winner Takes It All' - 'Tell me, does she kiss/ Like I used to kiss you?' Which girl hasn't wanted to ask that question? Previously, everyone had danced to Abba, but no one had listened to the lyrics. When I listened to a song such as 'The Winner Takes It All', I thought, 'There's a story there.' I sound like a right Abba nut, don't I?"
But even the tenacious Craymer couldn't persuade Bjorn and Benny to agree to the show. "They weren't interested. I'd meet them every three years and say, 'I'd still like to do this,' and they'd go, 'Yadda, yadda, yadda.' But by 1995, the Abba Gold album had come out and sold millions, and they felt more sure of themselves. Bjorn finally said, 'You're right.'"
Craymer got together with the playwright Catherine Johnson, who came up with the show's central idea of the bond between a mother and daughter. In her diary, Johnson recorded an early script meeting with Ulvaeus and Andersson: "Abba Gold is playing - I am singing along to Abba with Benny and Bjorn! Persuade Benny to rifle the loft for an Abba T-shirt, which I pretend is for my daughter. It's for me really."
But none of this explains whyMamma Mia! has struck such a chord globally. For Craymer, the secret lies in the fact that - unlike We Will Rock You (Queen) or Tonight's The Night (Rod Stewart) - there is a credible narrative thread linking the songs. Mamma Mia! has an organic story-line; it's not merely an excuse for a gratuitous night of Abba's greatest hits. Indeed, Abba aren't even mentioned in the show. "If it had just been the story of Abba," Ulvaeus believes, "people would have said, 'Can't you think of anything else?'"
Ulvaeus had an unhappy experience with the Broadway production of Chess, and it did not run as long as expected. "What I understood after Chess is that the story is number one, number two and number three, as they say on Broadway," he says. "A lyric should take a story forward, and a lot of pop songs are static - they have no drama in them whatsoever."
Johnson's principal concern was to blend the songs seamlessly into the narrative. "We didn't want to have those awful clunky moments where people burst into song," she says. "I worked to get the story and the songs to work together."
The other huge draw for Mamma Mia! audiences - one that has made it a hit everywhere from Sydney to St Louis - is that its plot resonates with all of us. As its director Phyllida Lloyd (now flexing her artistic muscles on Wagner's Ring at English National Opera) puts it: "In Catherine's ingenious story, the audience seem to be having a very particular experience: they are seeing themselves on stage."
It is fair to say that Abba had a spell of exile in the fashion wilderness in the 1980s. "The media deemed them naff," says Michael McCabe, Mamma Mia!'s associate producer. "And people weren't quite sure whether they liked them. But throughout, whenever 'Dancing Queen' has come on, everybody hits the dance floor, from grannies to grandchildren."
And Abba's record sales continue * * to prove the case. Even after securing nine British No 1s, selling 350 million records and making an estimated £250m, the group still shifts an astonishing 3,500 CDs a day.
Now, of course, Abba have been through the irony tunnel and come out as one of the coolest bands on the planet (their refusal to re-form has done their cred a power of good). Their rehabilitation was aided by the starring role their music played in movies such as Priscilla, Queen of the Desert and Muriel's Wedding.
These days people come up to Ulvaeus in the street to say hello. ("They always think they are being really original when they say, 'Thank you for the music...'") Critics, meanwhile, fall over themselves to praise the band's peerless talent for a melodic hook. Joe Levy, writing in Rolling Stone, said: "Abba had a gift for melody so prestigious that they couldn't stop themselves." Other musicians have been equally complimentary. Bono has called Abba "one of the best pop groups ever", while Nirvana said they would perform at the 1992 Reading Festival only after learning that the Abba tribute band Bjorn Again would also be on the bill.
Ulvaeus has never seen any of the hundreds of tribute groups that litter the back pages of The Stage, and which make a good living out of impersonating him and his fellow band-members. "I wouldn't dream of it. Life's too short. It would be so weird. We lend ourselves to tributes because there is no danger of us coming back and spoiling their act - 'Why did you have to come back and ruin everything?'"
Abba split in 1982. "All four of us felt it was the right moment to end," Ulvaeus says. "We didn't think we had anything more to give, and there's something magical about eight years. A lot of groups have that lifespan. The Beatles lasted for the same period. Many groups go on, but they can never recapture the bubbling creativity of their early years."
Since the demise of the group, Agnetha Faltskog, the blonde singer who was Ulvaeus's wife during Abba's peak years, has lived the life of a recluse on an island off the Swedish coast. Known in her native land as "Garbo II," she recently broke her silence to announce her first album for 17 years, a compilation of 1960s covers entitled My Colouring Book, although she's since gone to ground again and refused to do any promotion for it.
Her fellow singer, the red-headed Anni-Frid Lyngstad, who used to be married to Andersson, has lived in Switzerland since the death a couple of years ago of her second husband, a German prince. Like Faltskog, Lyngstad is a grandmother. "One night at Mamma Mia! she came on stage and sang 'Dancing Queen' in the finale," Craymer says. "She's a real dynamo."
Despite rumoured fall-outs, the former band-members keep in touch. "Of course, I feel an emotional tie to the other three," says Ulvaeus, who confesses that the only time he listens to Abba's music now is when a song comes on the radio. "When one has gone through such a fantastic thing together there is something very special: no one else can have it. We're actually the best of friends."
Although he is now married to Lena, with whom he has two daughters, Ulvaeus remains on good terms with his ex-wife. His most lasting friendship from the group, however, is with Andersson. Some 40 years after they first met at an outdoor musical festival, played Beatle songs together all night under a tree and formed a band called Festfolket, they are still very close. They are collaborating on an English version of their Swedish musical Kristina from Duvemala (1995).
"The reason our professional relationship has endured is that we are very good friends who trust each other on every level," says Ulvaeus. "I was like the brother Benny never had, and I suppose he was that for me."
Life has been good to Ulvaeus, who is approaching his 60th year. Apart from a touch more grey in his beard, he scarcely looks older than the day "Waterloo" changed the face of pop. Most people would be content with one massive career in music, but he has enjoyed two (thus far). "In this business, it all begins and ends with a song," he says. "Without that, no one is anything."
His legacy in Mamma Mia! looks set to run and run. The show works, according to Michael McCabe, because "the music reminds you of a carefree time before mortgages, bills and divorces. Mamma Mia! is a throwback to a time when life was easier. Abba are part of all our lives."
Judy Craymer agrees. In her view, the show has lasted because "it's not pretending to have a deep message, or be a Greek tragedy. When all's said and done, it's a show that makes people feel good." So could Mamma Mia! become The Mousetrap of musicals? "That would be funny, wouldn't it."
On the way out of the Prince Edward Theatre I spot the hen party again. As they pile back into the limo, the bride-to-be, wearing the fake tiara compulsory on such occasions, shrieks: "What a show!" She's clearly not alone in that sentiment.
'Mamma Mia!' is at the Prince Edward, London W1 to 22 May, transferring to the Prince of Wales Theatre, London W1 on 27 May (0870 850 0393)Reuse content