What madness is this? There is a sign taped up outside the Academy officially banning glowsticks from the Klaxons gig. Inside, security guards take fluorescent candy from crestfallen kids. Just over a year ago, people were actually handed free glowsticks on their way into Klaxons gigs. Having named themselves after an air horn, Klaxons played gigs awash with the lurid colours, smiley T-shirts and gurning faces of a putative new rave movement.
How success changes things. Klaxons, it seems, no longer have any need for little neon crutches. Their debut album, Myths of the Near Future, went platinum, and unexpectedly whisked the Mercury Music Prize from under the much-photographed nose of Amy Winehouse. Myths wasn't all that ravey, really; there were bits of everything from Blur to Tears For Fears in there. Having spent the year touring ferociously, they've survived broken limbs (singing bassist Jamie Reynolds stage-dived at a French festival) and amorous Brazilians (goth-haired guitarist Simon Taylor-Davis steps out with CSS's Lovefoxxx) to end their victorious year with two nights at London's Brixton Academy. They probably don't want anyone losing an eye to a bit of pastel plastic.
The danger is brought home when the support act, electronic duo Simian Mobile Disco (increasingly known just as SMD), arrive on stage. Even before the first abstracted bleeps of 'Sleep Deprivation' drip out of SMD's modular synth pod, the duo get pelted with contraband glowsticks. It's a friendly gesture; SMD and Klaxons go way back. The cuddly bedhead bobbing at the back is hip producer-about-town James Ford, who helmed Myths of the Near Future. Twiggy blond Jas Shaw flits about the front of the pod, operating what looks like an old-fashioned telephone exchange.
As the bleeps coagulate into a hook, a proper rave breaks out down the front. It's only 8.45. Emboldened, Ford and Shaw crank out toothsome deconstructions of 'It's The Beat' and 'Hustler' (two fine singles) and deploy quivering acid house builds. They are quite sensational - better, even, than Klaxons. That's where the rave ends. Although you can still jump around to Klaxons (and everyone does) the trio are not the fluorescent striplings they once were. Their set still starts with 'The Bouncer' - a cover of a lurid early Nineties rave track - but tonight it sounds more like Napalm Death than some swivel-eyed call-to-drugs.
Where once they were powered by a drum machine, Klaxons' live drummer, Steffan Halperin, is now a fully-fledged member of the band. Tour-hardened, they have turned into a rock band with added whoop-whoop noises. Glowsticks are out. Capes are in, and strange tasselly apocalyptic leathers that make lurching frontman Jamie Reynolds look like a Mad Max extra. Reynolds has been speaking recently about how the new album is taking on a European prog rock direction, and you fear a little for the future. No good can come of prog. Capes ruined Air.
For now, though, in the absence of any new music they're willing to share, Klaxons whip through the hour-long set they've been reshuffling for roughly 18 months. 'Atlantis to Interzone' instantly reorganises the front half of the audience. The delicate flee in search of sanctuary, the mentalists throw themselves around like netted squid. Every few minutes a lurching, sweaty, soppy Reynolds tells us how glad they are to be home.
They may have lost their neon glow, but Klaxons's wired pop remains largely intact. They always were art-pop imps in neo-rave T-shirts, and their potent lyrical mish-mash (drawn from Aleister Crowley, Thomas Pynchon and William Burroughs) probably turned the heads of the Mercury judges as much as their tumbling tunes. There wasn't - and still isn't - any band around who sound anything like Klaxons. A sensational version of the Crowley-toting 'Magick' is an unexpected high: weird but utterly accessible.
The real skin-prickler, though, is 'Isle of Her', a creepy chant-along. The added rock weight is a revelation here. We all know Reynolds, Taylor-Davis and singing keyboard player James Righton aren't proper occultists, but 'Isle of Her' foregrounds their latent tribal mojo. If some of that voodoo makes its way into the new album - only half-jokingly dubbed Myths of the Near Past - then we can probably disregard the bad omens in the leather epaulettes.
Three to see
London O2 Arena, Monday
Postponed due to Jimmy Page's broken finger, the Ahmet Ertegun tribute gig finally goes ahead.
Birmingham NEC, Mon; Bournemouth International Centre Tues; Newcastle Arena Thurs; Glasgow SECC Fri and touring
The 'Umbrella'-toting R&B star jets in for a proper tour.
London Shepherd's Bush Empire, Wednesday
Everyone's favourite Tuareg blues-rockers play a one-off date; they've just announced a spring tour.