Coldplay, Crystal Palace, London

So, next time you hear the statisticians telling you that Coldplay are the most popular band since The Beatles, and the superfast sales of X&Y mark some sort of zeitgeist-defining moment, take it with a sizeable pinch of Tesco Table Salt (84p, a couple of aisles away from Coldplay): many of these sales are impulse purchases from people who don't love music enough to enter a record shop, but fancy something non-challenging to whack in the car stereo during the school run or the drive home from work.

And, next time you hear Chris Martin denouncing global capitalism and urging us to Make Poverty History, don't forget that the aggressive marketing and rapacious pricing policies of global capitalism have done a fair bit to consign Martin's own poverty to the dustbin of history.

This isn't to say that he's a hypocrite (although it's notable that there's no MPH stall on the Twisted Logic tour), nor that he should wear a hair shirt just because he's successful (although one can imagine him doing so, if it came in a tasteful shade of beige). Indeed, part of Chris Martin's sellability is his self-deprecating, "What, this old thing I threw on?", three-days' stubble, ordinary-bloke factor. He may often be compared to Bono but Martin's public persona has a lot more in common with that of a different Live Aid icon: Phil Collins. His breezy informality, his disingenuous lack of pomposity, his "only meee, just a geezer like you" shtick is uncannily similar (although it must be said that Martin is more likeable).

He is self-effacing - or, perhaps, careful - enough to emphasise that Coldplay are a band, not just The Chris Martin Four. Genuine or false, 44,000 people have bought into it, and have braved the nightmare of reaching the outskirts of Croydon to squint at the giant screens in this athletics bowl. So perhaps there is something of a Band Of A Generation zeitgeist at work here.

This is the go-surfing-in-Newquay demographic; the "I don't believe in organised religion but I believe in spirituality" demographic; the watch-Big-Brother-but-don't-take-it-too-seriously demographic; the "Jamie Oliver's a breath of fresh air" demographic; the voted-Blair-despite-the-war demographic. And Tesco-rockers Coldplay are their fave band. They love them to bits.

So much so that, three songs in, when Martin opens his lips to sing "Look at the stars...", he's stopped in his tracks by a mass singalong, and looks genuinely gobsmacked. (The spectacle is repeated during "The Scientist" and "In My Place".) Martin has grown into a deft crowd-charmer. There's a clever little Richard Whiteley tribute, some topical banter (dissing Crazy Frog, bigging up Live 8), some eye-sizzling lights and lasers, some spectacular piano-diving and some comical mic-stand twist-dancing, and the demographic lap it up.

What is their secret? What is their message to their congregation? "You're in control," Martin sings on opener "Square One", "is there anything you want to know?/ The future's for discovering/ The space in which we're travelling..." These are the sort of benign, banal, optimistic platitudes that made Moby a millionaire, and they continue throughout: "Look at earth from outer space/ Everyone must find a place" and "You're part of the human race/ All of the stars in outer space/ Part of a system, a plan." I can't help suspecting Martin of being a secret god-botherer.

Perhaps it's in the sound. "I could write a song a hundred miles long," Martin sings during "Swallowed In The Sea", and this - the all-consuming desire for enormity (greedily swallowing up pieces of Doves and Kraftwerk along the way) - does seem to be their guiding aspiration: to Coldplay 2005, size is everything. X&Y is, if nothing else, a BIG record. And they don't come much bigger than "Fix You", X&Y's epic centrepiece, which closes the show and explodes in a burst of fireworks over SE19.

The following night, another 44,000 don't need gunpowder: the skies provide fireworks of their own as forked lightning stabs the sky. Me, I'd say it was nature. Chris Martin might say it was God. The Coldplay Demographic might say "It's, you know, a spiritual force kinda thing." Whatever, it was bloody great. And you can't buy it in Tesco's.

Reebok Stadium, Bolton (01204 673600), Monday and Tuesday