Primal Scream, Eden Project, St Austell, Cornwall

There's an immutable law of rock'n'roll dictating that the longer a rock band stays together, the more its creative energy will dissipate under the parallel burdens of musical complacency and conflicting egos. Defiantly celebrating their 20th anniversary this year, Primal Scream have so far suffered from neither of these.

They may be in their forties now, but the rebel spirit lives on in Bobby Gillespie. All skin and bones, lank hair flopping down to his shoulders, he was wearing Iggy Pop's silver trousers and clutching the mic-stand with both hands like Joey Ramone. This is probably the only front man who still begins a show in 2004 with those hackneyed words: "Do you wanna hear some rock'n'roll?"

Nearly 4,000 Cornish fans and holiday-makers did, and in a venue dedicated to recycling, who better to deliver it than Primal Scream? Back in 1984, they played Sixties-influenced jangly indie-pop, then defined the dance-rock crossover revolution with 1991's landmark Screamadelica, before making a wild regression into Seventies retro-rock, and finally finding their true voice in the past decade. Their recent trilogy of albums - Vanishing Point, Xtrmntr and Evil Heat - refined the dance-rock hybrid into what Gillespie terms a fusion of "weird electronic-psychedelic music" and "insane, explosive white-light rock'n'roll".

This show was drawn almost exclusively from those three albums, with the exception of crowd-pleasing diversions for "Rocks", "Jailbird" and a gorgeous gospelly rendition of "Movin' on up". The Eden Project is perhaps better suited to some of the summer's more mellow performers, such as Brian Wilson and Air, than the Primals' filthy rock'n'roll. But, even with half the audience picnicking on the grass with their children, they still made the ghostly biomes shudder with their intensity.

"Accelerator" and "Sick City" showcased the Johnny Thunders-style guitar licks of Andrew Innes, resplendent in a white suit and hat that made him look half-pimp, half-preacher. A rabble-rousing "Miss Lucifer" - The Stooges remixed by the Chemical Brothers - blended into "Shoot Speed Kill Light", driven by Mani's propulsive bass; in this setting, "Burning Wheel" sounded more than ever like a post-techno update of Pink Floyd's "Set the Controls for the Heart of the Sun".

The psychedelic jam of "Kill All Hippies" gave Martin Duffy an opportunity to explore his keyboard effects before the motorik rhythm that drives Detroit kicked in, reminding us that there's a powerful dance sensibility underpinning the sound. Best of all, on "Kowalski", a subterranean symphony celebrating speed, and "Swastika Eyes", a perpetual highlight of their live show, the Primals seamlessly amalgamated rock and dance cultures into a pulsating whole. Lights flashed, sirens bleeped, glam-guitar power-chords and funky fuzz-basslines slashed through relentless techno rhythms, and Gillespie howled his sloganeering lyrics, condemning America's "military-industrial illusion of democracy" with snarling, sarcastic fury.