Verdi’s Les vêpres siciliennes is his least performed mature opera, even in its more familiar version as I vespri siciliani. So mounting it with a top-ranking cast and an interesting production is just what the Royal Opera should do in a so far seriously under-celebrated Verdi bicentenary year. What has actually happened is that we have a first-rate musical performance and a dismally confusing, cluttered, pretentious and conspicuously consuming production by the most fashionable of Continental directors, Stefan Herheim, abetted by the set designs of Philipp Fürhofer and the ideas of his regular dramaturg Alexander Meier-Dörzenbach.