Suddenly, the lights in the purpose-built big top in the East End of London are dimmed and the talk of leveraged takeovers and management buy- outs is stilled. Over the PA, a voice calls out: "are you ready to rock, you party people?" It appears to have an inexplicable Swedish twang.
A spotlight dances across a set of golden curtains which are drawn back to reveal two women standing cheek-to-cheek in white glittery mini-dresses and thigh-high leather boots. They are flanked by a pair of bearded men dressed in white Mao jackets. You double-take for a moment, thinking you may have wandered inadvertently into an S&M show, until the foursome strike up the unmistakable tones of "Waterloo". Abba are dead, long live the tribute band.
Over the next hour and a half, Fabba send the legal eagles wild. Casting aside their earlier inhibitions, the lawyers do their best approximation of letting it all hang out to the greatest hits of the Swedish supergroup. They take particular delight in imitating the band's celebrated poses: back-to-back during "Knowing Me, Knowing You", wagging their fingers at each other for "Honey, Honey", circling one another with hands on hips in "Voulez-Vous". Some of the solicitors are so relaxed, they unknot their bow ties. Even the stilt-walkers get involved, miming broken hearts during "SOS". For an all-too-brief 90 minutes all 3,000 of us are 13 again, dancing our socks off at our first school disco.
The band leaves the stage after "Dancing Queen" to cheers that could be heard as far away as Stockholm, and the DJ puts on "Superstar" by the Spice Girls. The song empties the dance-floor faster than a stink-bomb. There is just no following Fabba.
Fabba are only one of up to a dozen groups - others include Bjorn Again and Voulez Vous - who are earning a living out of impersonating the Swedish pop gods. With a six-figure annual turnover, Fabba get through more than 200 gigs a year. In the past few months they have played in Bahrain, Jersey, Althorp House, the Conservative Party Winter Ball and Bob Monkhouse's 70th birthday party. On New Year's Day they were the first act to appear on Channel 5 after Big Ben had struck 12. Next month they play the Forum in Kentish Town, a venue that is the last word in trendiness.
Fabba's mentors, Abba, are now more popular than when they split up 18 years ago. People who were fans in their schooldays are rediscovering the band all over again. It's like a thirtysomething rekindling an affair with a childhood sweetheart.
On 6 April, the 25th anniversary of Abba's victory with "Waterloo" at the Eurovision Song Contest, Mamma Mia!, a West End musical featuring 27 of their songs opens at the Prince Edward Theatre. And that day Polydor Records are also putting out The Singles Collection, containing all Abba's 28 original A and B sides. Hearing this news, Alan Partridge would think he'd died and gone to Abba heaven.
The rock critic Nick Barber reckons we have warmed to Abba again "because they went through such a long period of being desperately unhip. They came from the decade that taste forgot, they were Swedish, and they were associated with Eurovision - none of those things is helpful if you want to be fashionable. It's not easy to go from an uncool to a cool area, but one of the ways of doing it is to go through the `irony tunnel'. People will start to say, tongue-in-cheek, `I like flares', or `lava lamps' or `Abba'. And gradually, if the thing is any good, it will pass through the irony tunnel to become cool."
On tour with Fabba, we are not talking Rolling Stones LearJet levels of glamour. Before the lawyers' gig, they struggle into their impossibly tight costumes in a cramped portable cabin adorned only with a few plastic chairs and a cracked mirror.
So why do they do it? Is it just for money, money, money? They would rather talk loftily of an enduring passion for the music. Andy Skelton, who in a previous life won New Faces three times and toured with Eurythmics, was once in Bjorn Again but left in time-honoured Spinal Tap fashion after "musical differences". He now works full-time as "Bjorn", the electric guitarist and founder-member of Fabba. He reckons that "Abba's songs have never left the public consciousness. They have been played constantly on every gold radio station. They've been a subconscious background to people's lives since the Seventies. The tacky label has even helped Abba to get through the bad times; they've got mileage out of people saying they were a laugh. Also, the music stands up - it's universal and appeals across the age range. If you buy an ultra-trendy wedding-suit, it soon goes out of fashion. Tails are more timeless."
Which is just one reason why Abba are ripe for tribute bands. Another, according to Skelton, "is the catalogue. An artist with just two hits would be hard to do, but only Elvis and The Beatles have had more hits than Abba. You can be on stage for an hour and a half and the audience will know the words to every single song. You can't do that with most bands. Tribute bands enjoy what I call `the McDonald's Syndrome'. Rather than experimenting with sushi, people know what they're going to get. They're never disappointed, because they get what they expected."
While Fabba vehemently deny the suggestion that they are "anoraks", they certainly take what they do seriously. "We wouldn't want Abba to walk in and see us taking the piss out of them," says Skelton. "Abba weren't a comedy band, so we can't turn them into one now."
For all that, you have to have a sense of humour to do a job that involves dressing up in a white satin jumpsuit and putting on a Swedish accent which by their own admission contains "elements of 'Allo, 'Allo".
The band prove as much when I bid them farewell, finally exhausted by the high-octane pace of life on the road with Fabba. Is there anything you have not told me about your rock'n'roll lifestyle, I ask in parting. "Our drug problem," Skelton deadpans. "Being in an Abba tribute band gives you a dreadful herring addiction."
Fabba play The Half Moon, Putney, London SW15 on 26 March, The Irish Centre, Leeds on 31 March, The Alley Cat, Reading on 1 April, The Woodman, Sidcup on 10 April, The Half Moon, Herne Hill, London SE24 on 16 April, & The Forum, Kentish Town, London NW5 on 17 AprilReuse content