Xanadu (Southwark Playhouse)

Even camp as Christmas comes early these days. November’s barely even started and already there’s a semi-naked Greek demigod in a teeny-tiny toga onstage at the Southwark Playhouse – not to mention all the chiffon, rollerskates and legwarmers you could ever wish for. Ancient Greece meets the 1980s? It could only be Xanadu.

Xanadu is the film so awful, a movie publicist created an awards ceremony to honour its awfulness – a kind of anti-Oscars, known as the Razzies. The film damns itself: Olivia Newton-John, "the girl you loved in Grease" beams the trailer, and Michael Beck, "who thrilled you in The Warriors," in a roller-disco rom-com musical about Ancient Greek demigods descending on California in disguise. It sucked. Hard.

So Douglas Carter Beane’s Broadway version is basically postmodernism in motion: a tongue-in-cheek musical of a crap film based on an old movie adapted from a stage play. It delights in its own atrocity, playing corny lines at half-cock and obliterating any last trace of truthfulness.

There wasn’t much to begin with, this being the story of a dunderheaded street artist (Samuel Edwards) making out with the Greek muse of history, Clio (Carly Anderson), as they build their own rollerdisco. Carter Beane stilts the dialogue and adds the odd well-placed ‘whence’. Any more knowing and it would classify as omniscient. "A rollerdisco?" trills Clio. "How timeless!"

What Carter Beane nails is the simple joy of sitting on a sofa and scoffing at Hollywood schlock, but it’s not much more difficult than that. Anderson plays Clio like a lobotomised Barbie, relishing the dodgy Aussie twang, and Edwards shows lots of thigh. It’s all very bubble gum – imagine an Ancient Greek line of Bratz dolls and you’ve got the measure of Paul Warwick Griffin‘s production – but it could use queering up a bit.

The musical spruces a few things up along the way, chucking in a wry subplot about a pair of nasty muses, Melpomene (Alison Jiear) and Calliope (Lizzy Connolly), out to curse the pair with cupid’s arrow. Muses can’t love mortals, you see. They’re the real pleasure here: Jiear vamping it to the max, hootching her way through Electric Light Orchestra’s "Evil Woman", and Connolly, a superb comic sidekick, wonking every dance move and landing every line.

Musically, it’s much the same: a score, straight out of "the box called juke," that is like the purest feta. Newton John had a hit with "Fool", but it’s "Physical" you’ll recognise – and choreographer Nathan M Wright gives it all of the pelvis thrusting it demands. There’s a smart Andrews Sisters-Eighties Rock mash up, "Dancin’", well arranged by Andrew Bevis, but, in truth, it all gets a bit samey.

That goes for the whole thing, really. It’s one joke stretched over two hours (though it does contain the bitchiest Andrew Lloyd Webber burn ever written) and that gets thinner than a chiffon toga. Thing is, it’s also critic-proof. Clio calls it herself: "This is like children’s theatre for 40 year-old gay people." Well, quite.

Xanadu runs at the Southwark Playhouse until 21 November.