The glass-fronted kitchen units are bright yellow and filled with many different kinds of crispbread. On the work surface there is a wooden block on which sits a large Plopp and a knife with which to cut it up - Plopp, of course, being a popular Swedish chocolate bar. When Benny from ABBA walks in, though, it's a circular disc of crispbread that he goes for. But for the greying whiskers and an expensive suit, he's barely aged since the group dissolved in 1982. Five minutes later, Björn from ABBA pulls up in his Lexus. Given that he and Benny employ everyone in the building, it's worth noticing that Björn makes his own coffee. Along with the communal Plopp and an office dog called Bjork, all the signs suggest that Björn Ulvaeus and Benny Andersson's Stockholm HQ must be a nice place to work.
It's only after a few minutes that the nagging sense of something missing dawns upon you. But for a poster proclaiming the 1999 premiere of Mamma Mia! - Catherine Johnson's West End musical - there are no gold discs or awards to suggest that Björn and Benny's 1970s might have been unusually productive. It can't just be modesty, either, because you can't move for posters and discs relating to Chess, the 1985 musical they wrote with Tim Rice - and who remembers that?
"Actually," says Björn, deploying that impeccably precise English in which Scandinavians seem to specialise, "there aren't as many ABBA awards as you might imagine. For the main part of the group's lifespan, the critics despised us." Maybe that's why, aged 57, he seems so happy to receive them now. Last month, at the annual Tony Awards, he and Benny, 56, received two awards for the Broadway production of Mamma Mia! Two weeks ago, they arrived in London to pick up a Special International Award at this year's Ivor Novello bash, and treated the throng to an impromptu chorus of Fernando.
"It's better than receiving a Brit, isn't it?" Oh, yes, I assure him. The Brits are a bit cheesy, really. Stevie Wonder and Leiber and Stoller have won this one. "Good. That's what I'd thought."
Björn Ulvaeus has two abiding memories of the ABBA years. The first goes back to the group's Eurovision Song Contest victory in 1974. In the preceding years, Björn and Benny, along with the group's manager, Stig Anderson, had become obsessed with the contest - reasoning that it would be the only chance the group had of getting recognition beyond their own country. "Stig rightly suggested that the song should have an international theme, so we all came up with Waterloo. It's the feeling of having won that I remember more than anything else. Just sitting in a room the day after, discussing what we were going to do worldwide. Suddenly we had a sense of something beginning."
Everyone remembers the footage, of course - especially Björn's stage costume. Sporting a sparkling skintight satin jump suit with what appeared to be knee-length Cuban-heeled wellington boots, Björn looked so bizarre that security guards refused to let him pick up his composer's award at the end of the show. "They couldn't believe that someone who looked like that could have had a hand in the composition," he explains.
In truth, Björn had waited a long time to jump about on stage looking like a total loon. To understand why ABBA were so brilliant in the 70s, we need to grasp just how bad the 60s were for them. Björn spent the most exciting decade of the 20th century in the Hootenanny Singers, clean-cut, short-haired purveyors of indigenous wholesome campfire fare like Song Of The Birch and I'm Waiting At The Stack. In 1963, just as his group scored their first Swedish hit, Björn heard the Beatles. "In my guts, I instantly knew that was what I would rather be doing, but we were beginning to have some success, so we kept repeating the formula. I would have much preferred to have been in a band like Benny's."
Benny Andersson also had a fairly clear idea of what he wanted to do in 1963 - and the fact that, at 18, he already had two children with his girlfriend, Christina, wasn't going to stop him. He grew his hair long and joined Sweden's nearest equivalent to the Beatles, the Hep Stars. He shifts uncomfortably when recalling his first brush with fame. Benny was not a frequent fatherly presence.
"I felt very immature at the age of 16, but clearly I was mature enough to get a girl pregnant. Whatever I might want to think, the fact is that I chose to keep on working instead of being with my family. Which, as you can imagine, was a disaster for them. But I've been talking to the kids through the years and for some reason, they feel that I made the right choice."
"When Björn and I finally met," recalls Benny, "our bands were staying in the same hotel. We met under an elm tree in the middle of a nearby park. We figured it would be a good idea to try and write a song together." By the time they got around to it, it was more in an atmosphere of desperation than glory. The Hep Stars had split up, but the Hootenanny Singers hadn't. "I remember," says Benny, "thinking it would be great to make a record like Pet Sounds by the Beach Boys, but also wondering if I did, who on earth was going to listen to it."
Instead, they recorded the soundtrack to a Swedish soft porn movie, Inga, and plotted their next move. The details of what follow read more like the synopsis of an unmade early Woody Allen film than the genesis of a supergroup.
Agnetha Fältskog, who married Bjorn in 1971 and had already scored a string of self-composed hits in Sweden, had the most to lose from the arrangement. Björn convinced his new wife that a cabaret run might arrest his and Benny's sliding fortunes. With Benny now dating aspiring Norwegian jazz singer Annifrid Lyngstad (known as Frida), the two couples decided to put together a . . .comedy revue.
Hidden away in Björn and Benny's personal archive, there is a picture of them dressed as schoolboys with lollipops and little helicopter propellers on their hats. After a year of playing half-empty nitespots to Swedish businessmen, Björn and Benny wisely put their school uniforms away.
It wasn't until 1972, a year later, that they had the idea of making a record as a quartet. Given that the couples were near neighbours and were spending all their time together, this seems incredible. And even then, People Need Love was a world away from the breathless pop majesty with which they later became synonymous - an unsexy beer-hall clomp on which yodelling featured heavily.
Also, the group - who had so far traded as Björn & Benny, Agnetha & Annifrid - had yet to think of a proper name. That came a year later when Stig Anderson ran a competition for Swedish radio listeners to come up with something snappier. When the best names on the short list were Alibaba, Friends And Neighbours and Baba, Anderson took things into his own hands and proposed that the quartet be called ABBA. That this was also the name of a Swedish brand of canned fish didn't seem to bother him; nor did Björn and Benny's initial lack of enthusiasm. He wrote to the fish canners and asked them if they minded sharing their name with a pop group. "They wrote back and said it was fine as long as we didn't do anything that reflected badly on the fish industry." ABBA was born.
Time spent with Benny and Björn is like time spent with a married couple, as befits two people who have been working together for 36 years. Benny is the alpha male - taciturn and vaguely intimidating. He borders on truculent when asked about his private life. Björn often seems to direct his answers at Benny, as if keen not to misrepresent him. In Björn's head, you suspect Benny is still "the cool one."
Benny recalls the writing of Money Money Money: "It was originally called Been And Gone And Done It. I said, 'Do you think this is really the best you can do?' " Björn seems both embarrassed and flattered that Benny remembers the episode. Björn's second abiding ABBA memory focuses on their co-operation, too: "It has to be the day Benny and I were working on two separate song fragments. I was playing guitar and he was at the piano, just like we always were. Then we realised that if we slightly changed one of them, they formed a complete song. That was such a kick! I'll never forget it. That was when we got the melody to The Winner Takes It All."
"The songs became something of an obsession for us," admits Björn."Each song had to be different, because in the 60s, that's what the Beatles had done. The challenge was to not do another Mamma Mia or Waterloo," says Benny. From SOS ("Our first really exceptional song," says Björn), it was something that seemed to come incredibly easily to them. Not only had they mastered what people refer to as the ABBA sound, they were writing songs especially for it. Björn: "Agnetha is a soprano and Frida is a mezzo-soprano, and that choral sense of tension you get with them is what happens when they harmonise."
Björn eventually took sole responsibility for the lyrics. "It wasn't really a job I enjoyed," he recalls. "I wrote a few stinkers." Benny: "I've told the record company that instead of releasing ABBA Gold, they should put out ABBA Wood. . .but, you know, they're not so keen on it. I don't know why."
"I'd like to nominate Dum Dum Diddle for ABBA Wood," smiles Björn, referring to the infamous album track in which Agnetha bemoans playing, um, second fiddle to someone who is "only smilin'/ When you play your violin". Ouch. "I'd been working all night trying to come up with a decent lyric. And I thought, 'Well, I'd better take in something to prove that I've been working.' I showed them this song, thinking they'd say, 'Oh, no! We can't do that!'"
Benny: "And we said, 'Whatever - that's fine.'" He was improving, though. Also featured on 1976's Arrival album was Dancing Queen. Five years ago, when the Sex Pistols' 20th anniversary reunion tour came to London, John Lydon decided that the band should enter to the strains of Dancing Queen - the plan being to remind us how terrible music had become when the Sex Pistols came along. The idea backfired. On instant recognition of that piano flourish, the entire audience cheered and broke into spontaneous dancing.
Here are three wonderful yet ultimately trivial facts about Dancing Queen: (i) Benny and Björn were inspired to write it by the rhythm to George McCrae's smooth anthem Rock Your Baby; (ii) It bore the working title of Boogaloo, and for days no one in the group could work out a satisfying intro - at the last minute, Benny and Björn hit upon the idea of starting it halfway through the chorus "for maximum impact"; (iii) It is the most perfect pop song ever.
Björn: "The day that Benny and I finished mixing the instrumental track of Dancing Queen, I was so excited, I just could not rest. Agnetha was asleep and I just had to share it with someone, so I drove all over Stockholm looking for someone to play it to. Finally I ended up at my sister's house. I played it over and over again to her. We couldn't believe how good it sounded."
Benny: "It's nice if you can like a backing track, you know? But by the time it appears on vinyl, it's gone. It's over. You have no connection with it. You know that it's you, but you don't sit around thinking, 'Oh boy! Am I good or what?' It's not like that."
Björn has gone uncharacteristically silent. For him, I suspect it was a bit like that.
It's impossible to talk about ABBA without talking about the darkness that gradually pervaded Björn's writing from 1977. It's in the Bergmanesque shadow-world of I Have A Dream, a world in which believing in angels might be our best hope for accepting an uncertain future. It's in Knowing Me, Knowing You, in which two estranged lovers survey the debris of their relationship. At this point, Björn must have had an inkling that family life was not altogether compatible with ABBA. "We all hated touring," he says, "and we were always careful never to be away from Linda and Christian [their daughter and son] for more than a few days. But for Agnetha, it was really hard."
That became clear to all on the 1977 Australian tour, when the group was greeted with adulation of Beatles proportions. "If you look at ABBA - The Movie [the film shot on that tour], you'll see that she was never quite able to let go on stage. She was always a bit fearful - whereas Frida is clearly having a whale of a time," Benny recalls. In her 1997 co-authored autobiography, As I Am, Agnetha writes, "Sometimes it was awful. I felt as if [the fans] would get hold of me and I'd never get away again. It was as if I was going to be crushed. No one who has experienced facing a screaming, boiling, hysterical crowd could avoid feeling shivers up and down their spine. It's a thin line between ecstatic celebration and menace."
The year the ABBA movie came out, 1978, was also the year Benny and Frida finally married. Three months later, Björn and Agnetha divorced. Björn is keen to emphasise that "mine and Agnetha's divorce was never acrimonious. We just felt that we had grown apart." Agnetha is more elliptical. Referring to their marriage as "destructive", she says, "We all know that there is no such thing as a happy divorce. The reason behind our separation is one of those things I definitely don't want to go into."
A week after the couple spent their last family Christmas together, Björn met his current wife, Lena Källersjö, at a party. "I think," he avers, "that divorce can produce a very positive creative energy."
Most people, I tell him, find it hard to imagine why the group wanted to continue in such circumstances. "Well, I agree, it was odd in the beginning. I would come into the studio and I didn't know what she had been up to for the last two weeks, that kind of thing. But we were very professional about it. "
Did you not ask her what she had been up to?
"Hah-hah! No, I didn't ask her that!"
Abba's final two albums portrayed a man buried deep in the doubts and recriminations of his own interior world. Happy New Year, from 1980's Super Trouper album, was set at the end of a party where the "dreams we had before are all dead/ like confetti on the floor". On The Winner Takes It All, Björn wrote the lines, "But tell me does she kiss/Like I used to kiss you?/Does it feel the same/When she calls your name?" Then, in one of the greatest acts of sadism in the history of pop, he got his ex-wife to sing them. "I wrote that one very quickly," he says.
The way the song begins - "I don't want to talk" - it's like the slurred beginning of a drunken speech.
Björn: "Yes. I wanted it to be a bit like that.
Benny: "It's bloody clever."
"As a matter of fact," admits Björn, "I was quite drunk. And that's unusual, too, because it never works. Whenever you write drunk, whether it's music or lyrics, you look at it the next day and it's bullshit. But that was a good one. I remember presenting it to the girls, and there were tears, you know?"
Even the album's ostensibly cheerful title track began with the line, "I was sick and tired of everything/When I called you last night from Glasgow."
"I was especially proud of that one," beams Björn. "We had already finished the album, but we needed one more song. So I thought about those big spotlights that you get on stage. They're called super troupers, you see." He leaves a pause for effect. "But, you know, I also like the fact that the song could be about someone who is a super trouper."
As Frida's new punky haircut confirmed, her marriage to Benny was now on the rocks. Writing sessions at the group's summer retreat were yielding worrying results. The Piper saw Björn imagining the rise of some charismatic dictator in a distant land - with Agnetha and Frida's harmonies on the chorus treated to a sound like a procession of Nazi oompah-loompahs beating tin drums.
"I guess we were in a strange place," says Björn.
By the time the group's final album, The Visitors, appeared at the end of 1981, they had given up trying to pretend everything was rosy. Frida and Benny had by then divorced. Slipping Through My Fingers articulated Björn's regret at having prioritised work over Linda and Christian's early years. The title track sounded like Joy Division, and described the plight of "a Russian dissident slowly going crazy whilst waiting for that knock on the door. Somehow these were the characters I was empathising with." In terms of mood and psychosis, these songs were on a par with Pink Floyd's Animals or Radiohead's OK Computer. The sleeve showed them photographed in the reception room of some stately home, dwarfed by huge paintings of angels. All four members of the group are bathed in orange light; each is looking in a different direction.
"The sleeve designer," says Björn "was a close friend who saw what had happened in our lives."
"I thought he just liked the room," suggests Benny disingenuously.
Björn: "Yes, but it really reflects what was happening. Basically, we'd had enough."
At the time of Abba's demise, the extent of their legacy was unclear. The group never formally split - the public didn't care enough for it to warrant a formal announcement. They released a masterful farewell single, The Day Before You Came, and promoted it in Britain with a couple of glum TV appearances. Benny and Björn, of course, started hanging out with Tim Rice and decided that by using the tactical high tension of a chess tournament in the Cold War as a metaphor for failing relationships (heaven knows where they got that idea from), they might attain some of the critical acclaim owed to them.
In the 1980s, Björn and Lena moved to Henley-on-Thames and sent their children to a nearby public school. Benny remarried, developed a passion for breeding racehorses and released two albums of instrumental folk music. He and his wife also had two children. "This time," he says, "I was ready for it. It felt more relevant."
Imagining ABBA would gradually fade into insignificance, they licensed their back catalogue to a host of budget price record labels "for next to nothing". Throughout the 1980s, you could buy ABBA compilations at petrol stations and newsagents for loose change. "That was it as far as we were concerned."
For a decade, only postmodernists and pranksters seemed to ally themselves to the group's music. On their 1987 What The Fuck's Going On? album, the KLF, in their early guise as The Justified Ancients Of Mu Mu, sampled the entire intro and chorus to Dancing Queen for their track The Queen And I. When ordered to destroy all copies by Abba's publishers, they drove to Sweden in an attempt to find Benny and Björn. This, it transpires, is the first they've heard about it.
Björn: "Why did they do this?"
Um, they were making a statement about the nature of copyright.
"Were they stopped?"
Well, they came to Sweden, trailed by the NME, in order to explain their actions to you, but they couldn't find you. So they put all the remaining copies of their album on a bonfire.
"That's good," notes Benny flatly. Understandably, Benny and Björn seem sensitive to the derision of others. Their first reaction to the success of tribute bands like Björn Again was annoyance. "I thought I was being sent up at the beginning. I felt that talking in these funny accents in between songs was a little too much. But when bands like U2 get in touch with you and ask you to appear on stage with them, you realise that it's just degrees of affection. I think it took us a while to come to terms with that."
Surely, though, tribute bands and the success of Mamma Mia! is about people wanting an excuse to go crazy in a public place to ABBA songs.
"I think it's kind of sad, actually," ponders Benny. "When you hear those songs being covered by young pop groups. I mean, hasn't anything happened in the last 20 years?"
"What I like," says Björn, ever the diplomat, "is when you hear it in a new song."
Max Martin, the Swedish writer-producer who penned Britney Spears' biggest hits, seems to be a case in point. The strange hymnal harmonies of Oops! I Did It Again and Hit Me Baby One More Time have Abba's DNA all over them.
"Well, some of those hits were produced in our studio, you know. Take away the production and it's actually quite a folky quality. That's why it sounds unusual to English ears. It's Swedish music with an American production."
These days, it's unadorned Swedish music that forms the basis of Benny and Björn's work. They're currently working on an English version of Kristina Of Duvemåla, their three-hour musical based on Vilhelm Moberg's 2,000-page epic about Swedish emigrants in the early 20th century. "It would be nice," says Björn, "if we could take it to London, but we're not sure at the moment." He doesn't say so, but you get the impression that backers might not be falling over themselves to invest in such a project. The problem is, I tell him, that post-Mamma Mia! musicals based on the back catalogues of established pop groups are all the rage.
Björn Ulvaeus smiles. "Ironic, isn't it? But you either accept it or give in to it. And for me, that's not what life's about. You know, last year an American promoter offered one billion dollars to reform for an ABBA tour. When an offer like that comes along, you have to seriously consider it, because for that kind of money you can build hospitals. But then the four of us ended up thinking what kind of a year that would be - all the stress of disappointing people night after night. I could imagine the looks on the faces in the audience as they realised we had grown old." He shivers at the thought. "Really, there's no amount of money in the world that could persuade me to do that."