Indiepop has always been played by misfits, those fragile souls who don’t quite gel with the brash mainstream, but it’s rare to see the theory in the flesh. Edwyn Collins and Morrissey both made a career from being distinctly stylish outsiders, while even Belle & Sebastian look like they wouldn’t wilt under pressure if faced with an impromptu kickabout.

The Decemberists, however, wear their mistfit credentials with pride. Singer Colin Meloy, a slightly podgy mummy’s boy in a white blazer, could be Dwight from the American version of The Office. Guitarist Chris Funk lives up to his inevitably nerdish crazy guy name by sporting a pointed green army hat with a big red star on it, looking for all the world like a Russian pixie. Bassist Nate Query, meanwhile, would seem dapper in his homburg and vintage suit in any other company, but here looks like he got the dregs from the dressing up box. Only violinist Petra Haden (sister of Spain genius Josh, slo-fi fans!), in a smart black and white patterned dress, could sneak out of the venue without being mistaken for a cast member of “Geek! The Musical”.

Musically, The Decemberists reference the biggest misfit touchstone of them all – They Might Be Giants. “The Legionnaire’s Lament” could be a long lost cut from TMBG’s hugely underrated “Flood”, the romantic swagger and upbeat accordion conspiring with the tenor of Meloy’s accent (really, a dead ringer for TMBG’s John Linnell) to create precisely the kind of strolling folk that made the Brooklyn duo famous. There’s also a shared sense of goofish cabaret, most obviously evidenced in those outfits and some theatrical set pieces (of which more later), but whereas TMBG sometimes succumbed to one smartarse lyric too many, The Decemberists’ mostly melancholic core serves to reign in any wackiness.

For, make no mistake, lurking under this jaunty, geeky façade are a whole host of gloriously unhappy endings. Doomed lovers hurl themselves from Dover cliffs (“We Both Go Down Together”), the ghost of a child laments the loss of her mother and her life (“Leslie Ann Levine”), the crew of a ship end up in the belly of a whale (“The Mariner’s Revenge Song”). While Meloy trades almost exclusively in heartbreak and tragedy, very little is autobiographical – instead most songs tend to start with a first person declaration, setting up the scene (“I am an engine driver” for “The Engine Driver”, “I am a legionnaire” for “The Legionnaire’s Lament”, and so on). Hence the crowd can dance and sing to their misfit heart’s delight – it’s all theatre and storytelling, after all.

And dance and sing they do. Unlike at Clap Your Hands Say Yeah the week after, this isn’t a crowd straining to like the latest cool overseas import – it’s a crowd that caught the band at either the Water Rats or the LSE and are in love. When Meloy hushes everyone for “The Bandit Queen” and tells them to picture being at a campfire in the Rockies, fans yell back affectionately that it should be the Lake District. One guy even gets onstage to tell a joke. And the set piece for “The Mariner’s Revenge Song”, where Meloy pushes each band member over one by one and then gets the entire crowd to sit down, only works because this is an audience of friends, willing to play along.

They encore, fittingly, with a cover of ELO’s “Mr Blue Sky”. Another band of talented misfits untroubled by cool. A truly wonderful night.

Ian Watson