For 50 years this musical has been part of the New York theatre landscape. Japanese director Amon Miyamoto’s solid revamped version will last less than a month in London, not because it is bad — it is well performed, and Harvey Schmidt’s score is sweet enough — but because at the heart of this love parable about boy and girl neighbours, there is no heart at all, but a banal little message delivered by teenagers and parents from central casting. Americans must love a platitude.