Some Stephen Sondheim flops – Assassins, Merrily We Roll Along – received such admiration on revival that they became core repertory. However, London’s first Sondheim musical since the composer’s death in November is a show that not only got away but stayed there: Anyone Can Whistle, pulled after nine Broadway performances in 1964, remains an elusive curiosity. A measure of the mess it became is that the best song, There Won’t Be Trumpets, imagining how a Messiah may arrive, was cut in New York to save time, but, after becoming a cabaret standard, restored to the score.