Michael Billington on reviewers who join in the play
'Keep off the stage when you're on duty'"Imprisoned in every fat man," Cyril Connolly once wrote, "a thin man is wildly signalling to be let out." And inside every critic, it seems, lurks a performer struggling to escape. Driving into London's West End on Monday, I heard our own Tom Service previewing a standup routine he's doing for Red Nose Day. Half an hour later, I was watching the Evening Standard's Henry Hitchi…