I'd like to teach the world to sin

We're in the atrium of a sleek, modern five-star hotel that is actually in Moscow but could be almost anywhere in the world. In the bar, the man from Pepsi is unhappy. "It's like the Wild West out here," he says, "Everyone's a cowboy." Andy Woodford's company has been employed by the soft drinks giant to create events to mark a momentous occasion: Pepsi has changed the colour of its can. Astronauts in the Mir space station have posed with blue cans. And now Red Square is about to turn blue with a massive free concert featuring Walthamstow bad boys E17. At least, that's the plan. But in post-communist Moscow, the best-laid plans can go wrong. There was a soundcheck scheduled this evening but, at the moment, there is no PA system to soundcheck on. Every request made of the local promoter is met with a demand for another $8,000. Everything from minibus hire to extra security costs is exactly $8,000, no more and certainly no less.

The soundcheck shunts back to midnight, then to 7am. In the current boy-group boom, E17 are the bad lads. The schoolfriends from East London who broke all the teen group rules about being squeaky clean and apparently celibate - the ones you've read about in the tabloids, bonding with soap stars in airplane toilets. All four are married now, three of them with kids. Tony, John, Brian and Terry wear outsized clothes by Versace, Dolce & Gabanna, Calvin Klein and Yves St Laurent (I know this because they like clothes with designers' names on them in VERY BIG LETTERS). Despite the tattoos and the macho poses, E17 are not big lads. Brian, in fact, is positively tiny, a mere munchkin of a man. Perhaps that's why young women like him.

11am A few girls wait outside the hotel with soft toys and photos to give to the boys. E17 return from the soundcheck with news that there was no soundcheck. Again. The PA had finally been assembled, but then it rained, and no one had thought to cover it up. Last night, E17's affable, efficient crew worked all night at the site to make the gig happen. At one point, they asked for food, and the promoter looked bemused. The crew suggested pizza, having seen a Pizza Hut nearby. The Russian left, returning a few hours later with a box of frozen pizzas and a bunsen burner. "How could this happen?" asked a crew-member. "It all started," replied one of the Russians drily, "with the 1917 Revolution."

11.30am We're at the Soho Club, a sleek modern bar that is actually in Moscow but could be almost anywhere in the world. Journalists cluster round the chrome tables, sipping from blue cans. E17 are holding a press conference, but the journalists haven't mastered the art of questions about their favourite colour or whether they like Russian girls. Instead, they begin a long, detailed interrogation about Pepsi's investment in Russia. They ask how much E17 are being paid. ("That's a bit personal!" Tony replies.) They ask if Pepsi is a health drink, and Terry responds with disarming honesty. No, he says. Water is a health drink.

The man from Pepsi is talking on the phone. "The PA is running," he says, without conviction. "The band are going to soundcheck. We have a show."

2pm A grey afternoon in Red Square, just by the multi-coloured ice-cream twirls of St Basil's cathedral. On stage, a giant blue bottle inflates, revolves, then droops flaccidly. A few hundred teenage girls have come to wave banners, scream and watch the soundcheck, and E17 rise to the occasion by giving them a four-song set. It sounds great. The man from Pepsi sighs with relief. "We have a show," he says, and almost sounds like he believes it.

Tony Mortimer is the brightest of the E17 bunch. He writes the songs. He sings lead vocal on many of them. He's the one that doesn't look like a cartoon. Back at the hotel, I ask him if they're pleased about the demise of Take That, and he admits they are. It's been hard singing in their shadow. When E17 started out, their manager Tom Watkins (formerly of Bros, Pet Shop Boys) played them a video in which Take That lay on the floor and got covered in blancmange. "And we really laughed. Because if that was the competition, then there was no problem."

Their confidence was misplaced, but three albums and a string of hit singles later, E17 are still together and Take That are busy launching solo careers and recriminations. E17 have lasted, they say, because they're friends. Because if one of them gets ideas about being a star the other three are there to knock him back. All of them still live within a mile of each other.

Every time I refer to E17 as a band, Tony gently corrects me. They're a group, he says. When he's writing songs, he doesn't have the guitarist agitating for a solo or the drummer's ego to worry about because all the others do is sing. Unlike Take That's Gary or Robbie, credibility isn't something he yearns for. "The worst mistake you can make is to say you want to be taken seriously, because as soon as you do, it's all over. I'm cool. I like doing what I do. I always wanted to be in a pop group. At school, I wanted to be a pop star and have the girls fancy me. The trouble is, I wanted the girls in my class to fancy me and I don't know where they are now. It's still 12-year-olds and I'm 25. But I'm not who they see. They see a picture, they see Tony Mortimer from E17, not Anthony from Walthamstow. Girls didn't faint when I walked by at school, so I know it's not me."

He says he would find it bizarre being in Oasis, all those boys in the audience admiring you, wanting to be you. "I wouldn't feel comfortable with that."

5pm A meet-and-greet. The rise of commercial sponsorship has created these bizarre occasions, when star employees get to mingle with the famous for a second or two. Pepsi's Russian executives form an orderly queue and each gets the chance to shake hands with an authentic East London bad boy and have their picture taken before being hustled on. E17 smile on cue.

10.30pm It's pouring with rain, but more than 65,000 people are crammed into Red Square. We're watching a sleek, modern, pop concert that is actually in Moscow but could be almost anywhere in the world. E17 have a great backing band. They have a fine set of pop songs with catchy choruses, and a surprising number of the crowd already know the words. (Later, John is to discover with horror that they don't get royalties from Russia. No one does. Most Russians get their music on the pirated cassettes that are sold everywhere, even in the airport gift shop.) E17 give a polished, professional but entertainingly uncynical performance. They aren't trying too hard to be clever. There are no tongues in cheeks here. They're having fun, and the rain-drenched audience in Red Square are having it too. The man from Pepsi smiles. "We have a show," he says.