Alpha Blondy, Royal Festival Hall, London

From the atmosphere in the Festival Hall foyer, it's unclear what we should expect from the legendary Jamaican producer Lee "Scratch" Perry's Meltdown festival. The dance-floor is empty, and Alpha Blondy's concert is, supposedly, a seated affair.But as soon as the Solar System, Blondy's backing band, takes the stage, the entire theatre, boxes and all, rises. By the time Blondy himself appears, sauntering onstage already some way into "Jerusalem", security has given up trying to keep the aisles clear.

Alpha Blondy is the biggest reggae star in the world. In his native Ivory Coast and across Africa he is a megastar, while the dreadlocked youth of continental Europe and Latin America revere him as one of the few high-profile Africans to have embraced Rastafarianism. Like Bob Marley, he is seen as an icon of international peace and understanding. His multilingual songs promote faith and reconciliation while attacking corrupt politicians and religious zealots. But also like Marley, Blondy is disdained by many "serious" reggae fans as too commercial or unJamaican. This has limited his success in Britain. So the invitation to open the Meltdown festival is an opportunity for Blondy to establish his identity here - though tonight it seems he's preaching to the converted.

Many Jamaican stars who have played London recently have turned up with a stripped-down band. Blondy arrives with his full 12-piece ensemble - no synth replacements for the horn section here. Their music is pure, high-energy roots reggae. Purged of the 1980s production values (too much echo on everything) that marred some of their records, almost every number in this largely greatest-hits set sounds better than the studio version. There are occasional veerings towards ska and the use of distortion effects on the guitars, but tonight they only serve to crank up the energy.

Blondy's voice marks him out as unmistakably West African - a plaintive, high-pitched wail, comparable to that of Youssou N'Dour. It is perfect for reggae, and for the blend of languages Blondy employs, switching effortlessly mid-song between English, French and Mandinga.

Blondy doesn't look like a superstar. Diminutive in dungarees, he resembles a slightly deranged child, alternating between an expression that denotes either back pain or inspiration, and crazy, off-balance leaping. This quirky stage presence offsets the serious subject matter of his lyrics. Between-song banter is mostly limited to howls and cackles, apart from a short introduction to "Peace in Liberia" and an announcement that the curfew has been lifted in Abidjan (the largest city in Ivory Coast). When the conflict there ends, the king of African reggae plans a celebratory concert. But for now, his inauguration of this year's Meltdown was pretty festive itself.