There are invigorating versions of Guys and Dolls, Oklahoma! and Cabaret in London " and some enticing new dramas coming " yet theatre risks being cut off from its past David Hare has argued this week that musicals are strangling the growth of straight plays in the West End. I have some sympathy with his point, but it is one that could have been made anytime in the past two decades, during which there has never been …