Bestival's fancy-dress tradition ensures some surprising sights, but few as unexpected as that of someone crowdsurfing to the xx. The trio seem pleasantly startled by the size and mania of the Big Top crowd that greets every minimal guitar line and murmured vocal like a stadium anthem. Bestival's constituency is getting younger and more energetic every year – 24 hours later, Tinie Tempah is another rising artist who brings the Big Top to hysteria.

Friday night's main-stage closing acts, Hot Chip and Dizzee Rascal, have both matured into expert festival turns, one increasingly fluid and poignant, the other, peaking with a laser-strafed Bonkers, almost absurdly hectic. But the festival's biggest crowd is reserved for Mumford & Sons on Saturday evening. Even a sceptic can't gainsay the populist power of their hearty, outdoorsy singalongs, suggesting by turns a folk Coldplay and an Ocado Levellers. Next summer, headlining slots will be theirs for the taking.

Veteran acts get a more mixed reception. While the Wailers can't fail with a benign trot through the Bob Marley songbook, the croakily charming Gil Scott-Heron is mellow to a fault. On Saturday night, Roxy Music are so keen to assert art-rock credentials that they reserve their hits, perhaps unwisely, for a stirring sprint to the finish. But Headliners Flaming Lips hold nothing back. Their set resembles a children's party orchestrated by Hawkwind and Doctor Who, turning frazzled acid-rock into main-stage fare by dint of Wayne Coyne's abundant charisma and an arsenal of props, including giant laser-emitting gloves. "Thank you, everybody, for being such freaks," says Coyne, as his band capture Bestival's spirit of youthful intensity better than anyone.