Each new audience generation has to discover it, and the central roles offer endless interpretative possibilities. Sir Anthony Dowell, who steps down as Artistic Director in July, is still remembered as the most tender of Romeos in the 1960s, alongside Nureyev’s very different reading. And now we have the miraculous Sylvie Guillem, whose Juliets have not merely set new standards for acting in ballet, but transformed it. No longer does dramatic interpretation seem pasted on to the steps Guillem is Juliet, with every spun-glass fibre of her body.

It’s a modern form of alchemy, no less.And as the ballerina has matured (she’s 35), so has her Juliet got younger. Of the Royal Ballet’s excellent current Juliets, none convinces so completely in the second scene, skittering around her nurse waving that silly doll. Most play it as if they truly love the wretched thing, which for a 14-year-old on the brink of arranged marriage is surely stretching it. Guillem, more subtly, conveys a teasing detachment, as if regressing deliberately – as children often do – for old times’ sake. And at the ball, how cleverly she lets us know that her grown-up dress and jewellery are novelties. It’s this kind of fine detailing that lifts the performance way beyond the technical. In fact, one soon stops marvelling at Guillem’s ballet technique.

It’s so sure that even the most life-threatening running-jump-with-a-backward-twist into Romeo’s arms comes across as a gesture of pure emotion.The Parisian Nicolas Le Riche is her Romeo, at 29 making his debut in MacMillan’s choreography. Properly boyish and loaded with unforced charm, he has the added bonus of being an uncanny physical match for Guillem, both facially and in the proportion and set of his limbs – a valuable asset in ballet Together they looked very fine. I was interested to see the ferocity with which he tore into William Tuckett’s sour and calculating Tybalt with his sword. This was none of your dreamy romantic who kills a man half by accident.