So Richard Dreyfus is unable to go on in “The Producers” when it opens in London in a few days. But wait – it’s not a disaster. Indeed, it could make the show a bigger hit, as Nathan Lane steps in to fill the role. “Whether or not Dreyfuss is a victim of the role, or the demands of the backers, or just bad luck – one thing’s clear: for those in possession of a ticket, it’s the equivalent of getting an unexpected upgrade from economy to club class. And, in many ways, the moment of panic couldn’t have arrived at a better time – everyone will now be pulling together harder than ever to ensure that it’s all right on the night.”