Kasabian, Brixton Academy, London

In a recent interview, Kasabian were getting very excited about the possibilities open to them as their tour buses improved. The Leicester rock band could have a microwave, DVD player, the works. And if that kids-in-a-sweetshop excitability makes them seem part of the same big gang as their fans, it's that "people's band" image that has helped them to rise.

In a recent interview, Kasabian were getting very excited about the possibilities open to them as their tour buses improved. The Leicester rock band could have a microwave, DVD player, the works. And if that kids-in-a-sweetshop excitability makes them seem part of the same big gang as their fans, it's that "people's band" image that has helped them to rise.

You can't blame them for wanting some home-from-home comforts, either. They've been gigging ferociously over the last year, from support slots with the likes of The Who, to a huge co-headlining tour with Chikinki, via numerous "guerrilla" gigs, whether at their farm in Rutland or at the Cabinet War Rooms.

And it's paying off, rapidly: the first time I saw them was at a sparsely attended gig at Cargo, a tiny east-London club, a few months back. Tonight, the 4,000-capacity Brixton Academy is stinkingly full.

Impressively, too, Kasabian have risen with few chinks in their armour. They're often lumped in with Manchester's "baggy" bands, primarily The Stone Roses and Happy Mondays, but neither of those had a reputation for being as "on it" live as Kasabian are tonight. The situation in the crowd could be described as "messy", but on stage, Kasabian are surprisingly tight and focused.

What's more, they have a little more colour to them than the "baggy" tag suggests, managing to switch smoothly from Space Invaders blips and rave-era beats to flyaway basslines and Stonesy rock'n'roll swagger. At best, they're even funky. "Processed Beats" has a very Mondays wiggle about it, "Test Transmission" is almost louche in its king-monkey lollop, and the loose and limber "Reason is Treason" is played with such guitar-at-knees gusto that you can almost overlook certain amusing similarities to Primal Scream's propulsive "Shoot Speed / Kill Light", and, in the mid-section disco break, "Swastika Eyes".

It is when Kasabian hit the awkward terrain of Messianic "big rock", though, that the pull of the bar kicks in. As their singer, Tom Meighan, bleats, "I want it, get on it, the troops are on fire", on an otherwise light-footed "LSF", he plays the rock'n'roll outlaw card with all the testosterone-laden fervour and Jesus posturing of The Verve's Richard Ashcroft, circa 1997. And that's no compliment.

Much of tonight's gig has the celebratory air of a Primal Scream all-nighter to it, but despite the people's-band pose, Kasabian never chance their hand at the kind of joyous Scream track - "Movin' on up", say - that can turn a gig into a communal event. Instead, they stick to clenched songs of urban aggro and blustery self-belief, which treat the business of getting high and getting loaded as a call to arms.

All that, and the band's Altamont chic, is a good rock'n'roll giggle for a while, but eventually, the earnestness of the delivery leaves you looking in vain for another point of entry into the songs.

Still, Kasabian's take on rock'n'roll trouble-causing is clearly hitting a nerve in those too young to have got it from older bands, and at least there's more fun, fluency and imagination to them than there was to Oasis.

As the Chemical Brothers-meets-The Charlatans mash-up of "Club Foot" closes the set, the roar of approval suggests that Kasabian have definitely caught their moment. They're gonna need a bigger bus.