Rarely do bands arrive in Britain facing such expectations as the Philadelphian quintet Sheer Mag. Two EPs, released on a tiny label, have stoked feverish hyperbole, aided by their policy of virtually ignoring the press and spurning the rest of the music industry – a good chunk of the crowd at the tiny Lexington is filled with people from indie labels, all of whom have paid to get in (as has the Guardian).

Their stock in trade is a rough-hewn take on 70s rock – there are what must contractually be referred to as “duelling guitars” in the style of Thin Lizzy, bursts of slightly funky southern rock à la Lynyrd Skynyrd, bits of choppy new-wave guitar and a whole lot of appealingly clunky pop heaviness that brings to mind nothing so much as an extremely low-budget Kiss.

Unlike any of those groups, though, there’s a political edge to Sheer Mag. Tonight’s encore, the anthemic Fan the Flames, has singer Christina Halladay addressing the forced cleansing of neighbourhoods through gentrification: “Trash on sidewalks, broken windowpanes / The pipes are leaking / They ain’t gonna fix it ’til it’s too far gone / They’re gonna wash us away / We’ve got to say.”

Fan the Flames is a truly terrific song, and there are a few others – What You Want, Button Up and Hard Lovin’, especially – but in truth there aren’t enough, yet. Two EPs in, of course, is far too early to make a judgment about a band, and when Sheer Mag lock into the riffs and Halladay’s screech hits its stride, they’re a burst of Technicolor excitement. But when they’re playing another song that feels like an album track from some justly forgotten band, it all goes a bit monochrome.

What happens next depends on them. If they’re happy to stay DIY, in small venues, they can carry on exactly as they are. If they respond to the blandishments of the label bosses, though, they’ll need to sharpen up and focus. They could be the next Kings of Leon, though whether that would be a good thing is very much open to debate.