Chris Martin: The stereo MC

That's MC as in Middle Class, you understand. The lead singer of Britpop's most lauded band, Coldplay, went to school at Sherborne. Worse, he doesn't drink, smoke and hasn't dated an All Saint. In snob-rock terms, he shouldn't have a prayer, let alone a tabloid headline. So how's he pulled it off? Over to you, Gwyneth...

Chris Martin doesn't drink. He doesn't smoke or take drugs. He was still a virgin at 22 and cut short a tour to sit his finals. Not very rock'n'roll is it? Even people who could hum his songs would have been hard-pressed to pick out the lead singer of the band Coldplay in a crowd – until recently. His only distinguishing feature was the facial expression of a little boy lost. So who was that sunny, confident front man who went up on stage to collect the first of two Brit awards on Thursday night and cheerfully challenged everybody in the room to a fight? OK, so it was a copy of a stunt the genuinely wild Robbie Williams pulled a couple of years ago, but totally out of previous character nonetheless.

The Brits is the kind of tawdry, self-congratulatory event this once wilfully unglamorous singer would have shunned in the past. His fellow nominees, Badly Drawn Boy and The Streets, both elected not to attend, although that could have been more to do with the ban on alcohol. But life has changed dramatically for Martin in the past two years. Coldplay are now one of the biggest bands in Britain – their debut LP Parachutes, released in 2000, sold eight million copies while their new album, A Rush of Blood to the Head, went in at number one, and is well on its way to reaching the six million mark.

His new starry demeanour is not all down to winning the Best Album and Best Group Brits, however, as anyone who has read a tabloid newspaper in the past six months will have guessed. Hollywood stars such as Jack Nicholson and Minnie Driver don't turn up to Coldplay gigs just because the band have recently become huge in America. They go because their chum Gwyneth Paltrow – yes, preposterously glamorous Oscar-winning Gwynnie – is currently dating Martin, propelling one of rock's most unlikely icons into a paparazzi-pursued world he could only have had nightmares about in the past.

They met at a party in New York last autumn and the rumours started immediately. That was Martin's fault: when Gwyneth came to watch the band at the Bowery Ballroom he dedicated the song "In My Place" to her, singing: "I was scared, I was scared, tired and underprepared, but I wait for you."

To be fair, no one seems more surprised at the relationship than Martin himself. "She's a big Hollywood star and I'm just the bloke from Coldplay," he gasped. Pop's principal odd couple have attracted an enormous amount of media attention, including repeated rumours of a split, with Paltrow's catty Hollywood pals whispering that Martin is simply a stop-gap to help the actress get over the death of her father. Last week Martin cheekily told reporters at the NME music awards that he'd never even met Paltrow. Yet the actress, who lambasted the clumsy seduction tactics of Englishmen immediately before their relationship became public, spent Christmas with his parents in Devon and was spotted moving cardboard boxes into his flat in Primrose Hill.

In some ways they are well matched. Paltrow, zealous about healthy living, is said to be a homely girl who likes nothing more than a romantic night in. If that's true, then her new beau fits the bill. Martin's never been photographed falling out of the Groucho and has never dated an All Saint. It's not long since The Sun carried a story highlighting how often the singer had been seen out wearing the same moth-eaten coat (four times in a week); there was less tabloid enthusiasm for publicising his work with Oxfam, or the trip he made to Haiti on behalf of the Fair Trade campaign. Never mind that he doesn't like to drink, this is a man who once apologised to his devout father for taking God's name in vain on stage.

Martin's ascendance may not qualify as particularly rapid in these days when chart-topping pop bands are created overnight, but it was fast enough to prompt a severe bout of paranoia. Following the release of Parachutes the singer refused to do interviews for 18 months, resolving to stay at home and concentrate on his songs. Looking back, you can hardly blame him. As Coldplay albums flew off the shelves the media were laying into them with the kind of ferocity usually reserved for ex-Spice Girls. Alan McGee, the man who discovered Oasis, raged against a group of "bedwetters".

Matters weren't improved by Martin's apologetic demeanour. "Oh, I never meant to cause you trouble," he whimpered on the song that was played on the radio day and night. Pull yourself together, man, you wanted to scream. Instead of The Beatles and the Stones we now have Manic Street Preachers, Travis and Stereophonics: all-male, middle-of-the-road rockers with no wit. Coldplay were written off as whiny, middle-class pretenders whose privileged backgrounds gave them nothing to complain about.

The son of a teacher mother and an accountant father, Martin grew up near Exeter alongside four siblings. He attended Sherborne, the Dorset public school, where he listened to U2 and dreamed of becoming the next Bono. He went on to read ancient world studies at University College London and met his fellow band mates – guitarist Jon Buckland, bassist Guy Berryman and drummer Will Champion.

Martin still seems bothered by his background. Referring to himself as "a self-obsessed, uncool fool", he lamented, "I've got no story. We're just a bunch of students. I can't be compared with Liam Gallagher or The Sex Pistols, or anyone real."

Yet his plaintive moan has struck a chord with the masses – so much so that Martin was approached to write the theme tune for the Hugh Grant romantic comedy, Love Actually. He turned it down for fear of becoming "the next Ronan Keating". To his fans, Martin and his band delineate the triumph of the underdog. Nice boys aren't supposed to end up on top. At this year's Glastonbury Festival Coldplay will be sharing the bill with REM, the most worshipped band of the past decade. That may be only fair: Mendip District Council was on the verge of refusing the event a licence until its mood was swayed by a passionate letter from Martin, urging councillors to let "the best music festival in the world" go ahead.

Martin has also shown a rare devotion to his fans. When the band's concert in Atlanta was rained off, Coldplay trooped into the car park and performed an impromptu acoustic set for the few hundred fans who had begun queuing.

The band is so big now that Coldplay don't have to pretend to be cool. Their fans may be grown-ups who wish they were still students, but there are lots of them. Reviewers heaped praise upon their second album, commending soulful melodies and insightful, poetic lyrics. But they still have critics: last week a member of Massive Attack railed against bands unwilling to voice their opposition to war with Iraq lest it damage their American sales, and highlighted Coldplay as an example. A day later Martin came over all serious at the Brits, saying "awards are essentially nonsense and we're all going to die when George Bush has his way". It was undoubtedly sincere, but it was also PR that his girlfriend would have been proud of. The shy, gawky, quiet man of rock had discovered the confidence and timing to speak out in a way that he might not have dared to do before Gwyneth.