The famously tempestuous Romanian soprano is, we learn, living a separate life from her husband Roberto Alagna. If Opera's Most Romantic Couple is no more, will Brand Angela be terminally damaged? Surely a showcase performance in the South Bank's International Voices season would be just the thing to rally the faithful and reaffirm Ms Gheorghiu's spectacular star quality, but I must admit that by the time we reached the interval, I was beset with gnawing doubt.

There are horrors in the world so vile that few of us want to think about them. None more so than such cases as Josef Fritzl - or Jaycee Lee Dugard, or Arcedio Alvarez, or Raymond Gouardo, or Wolfgang Priklopil, or Marc Dutroux... but you get the picture. Cases where men abduct girls and turn them into sex slaves and father multiple children by them, often incestuously, hiding them in garages, basements, behind walls, sometimes for decades undiscovered, sometimes murdering them. Mostly you read that it happened, you shudder, and try not to think more about it.

To a bewitching, shimmering prelude, a back-projected astronaut plants a Czech flag on the lunar surface. So begins one of those evenings where you skip out of the theatre grinning and promising yourself that you will buy tickets for all your opera-disdaining friends.

It’s a let-down when a new production of an opera that spends two acts feeling dazzlingly invigorating and clever collapses in a careless mess in the third. My guess is that a key scene for the concept of English National Opera’s Turandot is when Ping, Pang and Pong - three very grand court officials - turn out to be Chinese cooks sneaking smokes up the fire escape at the Emperor Palace restaurant. It's a sharp idea, generating a sensationally visual production, but that fire escape's got to lead somewhere, and in the end it's nowhere.

There’s nothing like a bit of communal booing to sharpen your critical faculties. And Christof Loy’s new production of Tristan und Isolde at the Royal Opera House last night received wave after wave after wave of it. An ocean of boos almost as deep and profound as the Wagner that had just washed over us moments before. One boo surge from above, one boo surge from below, rivulets of bass-boos and piccolo-boos from the flanks, all lapping at the half-grinning, half-freaked out German production team on stage.