Les Savy Fav, Electric Ballroom, London

"This is a concert," Tim Harrington reminds us, "and we're going to smash this room to ashes." The singer has already abandoned his unhealthy looking vest to the crowd, the nipple peepholes he gnawed in it earlier maybe adding to its attraction. He's bald and bearded, the roll of fat around his stomach suggesting just the right amount of appetite.

Peering down on us like a benign ogre, he reminds us of our good fortune. "Sometimes you have to see Kings of Leon..." Instead of which we have this tireless showman, who improbably somersaults into the crowd, in sync with his band Les Savy Fav's tumbling tune "Sleepless in Silverlake". His boots miss every head, in a miracle of mutual self-preservation.

This is exactly what everyone has come here for. In the 15 years since they met at art school in Rhode Island, Les Savy Fav have forged a reputation where little less than a razed room will do. They have been key, cult figures in their adopted Brooklyn home as it became America's alternative rock hotbed, and massively influenced Bloc Party here. Tonight's song titles – "Excess Energies", "The Sweat Descends" – describe the hard partying they stand for.

Harrington is, of course, always the centre of attention, as sweat pours down his mighty back as he dangles head-first from rigging he's just fearlessly scaled, or he changes into a checked kaftan and wig to resemble a leprechaun bandido. But in keeping with the values of Les Savy Fav's post-hardcore punk pop music, this just means his constant commitment is at the band's core. He understands the spectacle and ritual of rock'n'roll shows. Most importantly, he knows they are democratic. During "Equestrian", he becomes a centrifugal force that pulls in the whole crowd around him, touching and talking to them, leaving delighted grins in his wake. It's been a happy, mature wild night.