In theory, 2003 was the White Stripes' year. Their fourth album, Elephant, sealed their transition from garage band to global phenomenon. Yet lately, Jack White has seemed concerned about the future. The White Stripes are a self-consciously limited band: they play primitive blues while dressed in red, white and black. Now that everyone has got the general idea, what do they do next?
Tonight's gig offers no answers. The stage is covered by what appears to be a special colour-coordinated carpet, the only sign of the White Stripes' increased fortune. Otherwise, it is business as usual: primitive blues, red, white and black clothes. Jack White maintains his aw-shucks persona between songs, proudly displaying his nerdish knowledge of rock arcanum. He dedicates the gig to the Liver Birds - presumably the long-forgotten Scouse beat band of the 1960s, rather than the Scouse sitcom of the 1970s.
The lack of progression does nothing to render the show any less thrilling. White's guitar and voice have lost none of their visceral power through mass exposure: Hotel Yorba is still gleefully exciting, their cover of Dolly Parton's Jolene still emotionally wrenching. Not even the most gullible fan now believes Jack White and drummer Meg are brother and sister, but the interplay between them is still strong. He bellows into a microphone inches away from her face, foam dripping from his mouth. She stares impassively at his efforts, head thrown back, eyes half closed, radiating alluring indifference. It is compulsive viewing.
After a startling encore of The Hardest Button to Button, Jack White ventures to the front of the stage with a delighted smile. Momentarily, at least, the question marks over the duo's future seem to have vanished.
· At Alexandra Palace, London N22, tonight. Box office: 020-7734 8932. Then touring.