The return to Britain after some twelve years of the French avant-rockers MAGMA (Bloomsbury Théâtre, Thursday through Saturday) might just have been a story in itself. But there's another twist: The promoter is Steve Davis, snooker pro turned cultural dilettante. "You could say I am indulging in a passion," he says. You could also say that Davis is rescuing Thatcher's Arts policy from the dogs: private sponsorship at the 'sharp end' of contemporary culture has, until now, been largely nonexistent. Magma is also a passion: drummer/pianist and leader Christian Vander has dedicated himself to nothing but over the last seventeen years. More so than any of the current crop of European avantists, Magma's music demands that you accept it on it's own terms. The amalgam of rock, opera, spirituals and jazz outstripped all formal references, a soundtrack to Vander's tale of man, myth and magic, delivered in an invented phonetic, as opposed to semantic language. In the studio they are now way past their best: compared to the classic 'Mekanïk Destruktïw Kommandöh', their latest 'Offering' (Seventh: import) sounds flabby and indulgent. Live wise they have always been a force to be reckoned with - powerful and peerless.