While roadies who look suspiciously like mum and dad set up the stage before young rockers Smoosh grace it with their angelic presence, there's apprehension in the air. Normally, the crowd of chin-stroking musos would only watch young girls perform if they were their daughters at the school nativity play.

Fears are swiftly allayed, though, when sisters Asya, 13, keyboards and vocals, and Chloe, 11, drums, ping on to the stage with far more enthusiasm than most bands would be bothered to deliver on a freezing night in east London. Grinning broadly and sporting a festive jumper adorned with snowflakes and reindeer, Asya delivers a swift but charming "Hi!", and their debut London show commences amid screams and whoops from women old enough to be their mothers in the front row.

With their almost identical looks - long blonde hair and toothy smiles - they are unmistakably all-American kids, and thankfully manage to stay on the right side of creepy, coming across as less The Shining, and more the Sweet Valley Twins go to rock camp.

They dive into Rad, their sunny, shameless pop'n'roll anthem, with lyrics about soccer dotted with upbeat "Yo! Yo!s". And while their breezy song may sound exactly as you'd expect, the darker La Pump is surely the masterpiece. The girls brim with extraordinary confidence as Asya yelps her way through the raw electro-punk tune, like Le Tigre's Kathleen Hanna minus the bitterness and histrionics.

Fearless stage veterans already, Smoosh's rock'n'roll lullabies veer from jazz to blues and punk all with the same clear concentration, occasional charming clunkiness and, of course, fun. Tossing their hair and laughing at the crowd, they make it all look so easy - in fact, they make it look like child's play.