Being a composer of contemporary classical music is a treacherous business. It's about the only art form in which stylistic choices can still force a creator into permanent exile. Two composers who have fallen foul of the British house style in recent decades and have sought musical asylum in America and Europe, Brian Ferneyhough and James Clarke, were receiving an extremely rare London premiere of their new string quartets at the Wigmore Hall last night. And you could see why Britain had shown them the door.