Religion, and a sense of the revival of belief, is such an important part of everyday life in the wider population that it is one of the stranger facts about contemporary theatre that so few plays tackle this subject. In fact, the last new British play to do this at the National was David Hare’s Racing Demon in 1990. Now, 20 years later, the same Cottesloe theatre space bears witness to a new play, which opened last night, about the same subject.

Somehow the title sounds more sonorous in Italian. Io Sono l'Amore is a big, fat, full-blown melodrama, a film with the button marked "passione" forced up to 11. It looks exquisite, is a glittering showcase for Tilda Swinton as the restless Russian trophy wife of a wealthy Milanese industrialist and is elegant in spades: the cuisine, the couture, the shoes, the decor, the diamonds, the lipstick, they're all to die for. So what if it's also just a bit kitschy around the edges?

It finally came just over three hours in. Ferruccio Furlanetto’s gouty Philip II leans his elbow on his chair and begins to grind his head into his right-hand like he's a human pestle and mortar. He first castigates himself for ever having thought that his wife, Elizabeth of Valois - who he suspects of sleeping with his son, Don Carlos - might have fancied his unyielding, aged presence, and then tries to sing his way out of his tortured predicament.