This is surely the most comprehensive opera ever written: four hours (including breaks) of pure theatrical slickness, ­gambling-hall scene, church scene, street scene, ballet, Traviata-meets-Carmen-meets-Queen of Spades-meets-Bohème, even a hint of Maurice Chevalier singing “Sank ’eaven for leetle girls”. It is overwhelmingly French, gavottes a gogo, and drowned in Chantilly. But if you don’t watch out, Massenet’s 1884 work can get heavy rather quickly. Ponder things too long and you unearth a grim world where women are motivated solely by money, men by sex. All is weakness, venery, greed, treachery, revenge. Luckily, the composer and his old-lag librettist, Henri Meilhac, chose to write (at least partly) a comedy – as Meilhac had done so man