When Hans von Bülow, conductor of the first Tristan, described Wagner’s hymn to love as a “bel canto opera”, he wasn’t making a joke at the expense of the composer who had stolen his wife Cosima. He was making a valid point about the long lines, for orchestra as much as singers, that Wagner wanted to be sung beautifully. That aspect of Tristan is easily forgotten by those who assume it is all about vocal heft.

As Ben Heppner and Nina Stemme (right of picture) demonstrate in the Royal Opera’s new production, a large, penetrating voice is a help, as is the ability to pace oneself. But it is still possible to make Wagner sound Italianate. You just need a conductor on the same wavelength, which Antonio Pappano clearly is. There is ample intensity in his reading, not least at the opera’s two climaxes (in the Prelude and Liebestod), but what he brings out is Wagner’s singing instrumental lines in Acts Two and Three, and the way the orchestra is designed to support, not overwhelm, the title characters in their most exposed moments. You might hear a Tristan as well played as this but I doubt if you’ll hear it as beautifully sung. Heppner is the opposite of forceful. Stemme rides the orchestra with regal lustre. Michael Volle’s hunky, noble-sounding Kurwenal and Sophie Koch’s spunky, sexy Brangäne (left of picture) make a romantic couple in their own right: you wish they had more to sing. Stage and pit are seamlessly linked, and the cast blossom in a supportive, collaborative environment.