Powder her Face, Royal Opera House: Linbury Studio Theatre, London

Powder Her Face has the dubious distinction of being the piece that brought fellatio to the operatic stage. The Duchess of Argyll's scandalous extra-marital tryst with "the headless man" – headless because the incriminating photograph was focused elsewhere – has added to the repertoire an aria that will never be lost in translation. It is the climax, so to speak, of a first act that long outstays its welcome and which makes one wonder what possible dramatic interest there can be in the saga of an idle, rich aristocrat growing old disgracefully.

The answer for the then 24-year-old composer Thomas Adès and his librettist Philip Hensher would seem to lie in the English obsession with titled celebrity. Carlos Wagner's outstanding production of this precociously confident but only intermittently successful chamber opera plays outrageously on our voyeuristic self-righteousness in matters of morality. The judge's summing up at the Duchess's humiliating divorce trial is delivered in a mounting frenzy of sexual excitement, in turn shared by those in the public gallery armed with flasks of tea and binoculars.

But it's the camply hedonistic first act that comes across as so relentlessly, lewdly, tiresome, with Adès rejoicing in exhaustive 1930s pastiches of sleazy saxophone slurs, and even a song-and-dance routine. There's a touch of Britten's Death in Venice about the multiple caricatures taken by the excellent Iain Paton, Alan Ewing and Rebecca Bottone, whose assortment of maids and waitresses are vocally characterised in a succession of hyperactive squeals.

The look of the show is fantastic. A steep white staircase fans out from a single doorway. The action is entirely, and precariously, played out on these steps, suggesting the Duchess's imminent tumble from grace and favour. Outsize reproductions of her cosmetics are strewn about like Pop Art sculptures. And in the key moment of that fellatio, a naked Adonis emerges from between the legs of her "headless man" as if to highlight the distinction between sexual fantasy and base reality.

The best of Powder Her Face comes in the final scene where Joan Rodgers' riveting Duchess clings in vain to her pride while Adès attempts to imbue her with an almost Straussian dignity. There's a wicked reference to Der Rosenkavalier as a society journalist presents her with a silver rose. Is this the mad scene the Marschallin never had?

To 22 June (020-7304 4000)