A snoozefest. Zzzzzzzzz. Pretty bloody boring – just a few of the predictions about Sigur Ros’s Latitude headline set from some of my colleagues and friends this afternoon. I have to admit that, after seeing Metronomy’s dancey geek-pop about half an hour before, the prospect of a bunch of deathly slow ethereal meanderings sung in a foreign language (or, of course, a completely made-up language) didn’t seem like the most appealing prospect.

As obvious as it may sound from the set-up above, as soon as the first submarine ping of “Svefn-G-Englar” begins it’s clear their set is going to be some spectacle. I remember hearing the track on a free NME CD about eight years ago and it’s still as powerful now as it was then, especially when Jonsi Por Birgisson lets out an amazing falsetto note at the end and holds it for what seems like at least thirty seconds.

Joined by their regular string section Amiina on the molten “Glosoli” , it suddenly hits me that Sigur Ros, unlike what seems like most of the bands performing this weekend, aren’t using any backing tracks. The number of instruments onstage is pretty impressive too, consisting mostly of glockenspiels, xylophones and other bizarre keyboard instruments alongside harmoniums, pianos, samplers, drums and guitars.

The songs might be about eight minutes long (on average, of course), but there’s enough going on to keep most of the audience occupied. In fact, this is the biggest crowd we’ve ever seen throughout the last three years at Latitude; amazing, considering their turnout appeared to dwarf Franz Ferdinand last night, an indie-pop band whose last album went to the top of the charts. Birgisson’s flamboyant get-up – feathers, glitter, stylised military jacket – probably helps entice some of the audience, of course.

Other highlights include the entrance of a five-piece brass band, who parade around the stage before settling in to their positions at the back of the stage, and the band’s backdrop, seven giant globes which changed colour throughout.

Interestingly, hearing tracks like the anthemic “Vio Spilum Endalaust” makes me think that this is the kind of music Coldplay wish they were making on “Viva La Vida Or Death And All His Friends” . The most anthemic moment comes during “that one from that David Attenborough thing” – sorry, “Hoppipolla” – where some of the crowd even sing along with the piano part and there’s a feeling of collective ecstasy possibly better suited to the ending of “Hey Jude” .

Ending with a powerful version of “( )” ’s “Popplagio” , which reaches a stunning four-minute crescendo reminiscent of post-rock compadres Mogwai complete with confetti cannons, Jonsi practically destroys the violin bow he uses throughout. It’s a surprising moment of grit and violence from a band who many, including perhaps myself, wrongly thought were masters of ethereal blandness, wielders of impressive but insubstantial smoke and mirrors. There’s something euphoric and heartening about Sigur Ros’ live performance tonight. Some of the band’s slightly more insipid recorded work might not stick in the mind long after the CDs stopped spinning but the thousands of people who were here at Latitude tonight probably won’t forget this in a hurry.

Tom Pinnock