Bernstein’s Candide is the operetta that ought to work, but never quite does. Voltaire’s featherlight cakewalk through human misery, set to tunes from the West Side Story guy: what’s not to like? And what can be so wrong with its twinkle-toed score that the combined rewriting efforts (and this is not remotely the full list) of Lillian Hellman, Dorothy Parker and Stephen Sondheim have all failed to make it work as theatre? For my money it’s the ending.