When Grace Bumbry stepped onto the stage at Bayreuth as Venus in 1961, opera magazines and conservative media were poleaxed by perplexity. Here was a beautiful young American singer, 24 years old, appearing in Tannhäuser, opposite Victoria de los Angeles and Wolfgang Windgassen, luxury casting even by Bayreuth’s standards.

Just one problem: Grace was black. Wagner was race-pure. The media wanted to know what the hell was she doing in these hallowed halls.

The audience provided the answer. It gave Grace a half-hour standing ovation and 42 curtain calls. Game over.

When Matthew Bourne put on an all-male Swan Lake in 1995, reactionary media gave him the same reception. Tchaikovsky wrote for ballerinas, didn’t he?

Bourne’s Swan Lake went on to become the longest-running ballet on Broadway.

Opera and ballet are all about illusion. That is why the Telegraph critic is utterly wrong when he argues: Fat and thin can be equally beautiful, but one has to make an audience believe. There are times when physical absolutes make this impossible.

Wrong, wrong and wrong again. We go to the theatre to have our preconceptions challenged. We want to see something different, to have expectations overturned. We want to hear great singers, regardless of colour, race, shape or whatever. We want the experience to override physical absolutes, as it did with Grace Bumbry, as it did with Matthew Bourne. That’s the way great art goes forward.

Rupert’s way leads only to the grave.