First Night: The Minotaur, Royal Opera House, London

When Birtwistle speaks, the world jumps to attention: his new opera for Covent Garden has come heralded with all the drums and trumpets the media can muster. And what a perfect topic for a man past his three-score-and-ten, but still at the height of his powers. While Picasso's minotaur self-portraits – which apparently inspired The Minotaur – reflect a nagging fear of failing potency, no such fear is to be sensed in this dark, threatening, and strikingly assured work.

Even before the curtain rose on Alison Chitty's electric-blue and black shoreline, with a black sail in the distance and mezzo Christine Rice giving eloquent vent to Ariadne's misery, we knew what to expect. Myths and monsters have always been a mainspring of Harrison Birtwistle's work , but here it's the tragic fate of the human half of the hybrid which he wants to focus on: condemned forever to kill the victims sent down to it in the labyrinth. Birtwistle's and his librettist David Harsent's delineation of the Theseus-Ariadne relationship – mutual mistrust, not mutual love – turns out to be of secondary importance; they dwell in the ancient story's world of rape, murder, and the frenzied pecking-out of entrails.

And also of dreams, for when asleep, this monster sings. But to get to this point, we first have to sit through 45 minutes of dutiful and over-literary exposition. Like Chitty's designs, Stephen Langridge's direction, is clear and uncluttered, and the music is quintessential Birtwistle, with surface complexity masking a monumental undertow. But Rice's long arias, and John Reuter's graceful answering ones as Theseus, don't take wing.

However, as Rice begins to sing of her Minotaur half-brother's conception, the music crackles with demonic energy: the moment when the beast stands revealed is a brilliant coup de theatre. The drama is now both wonderful and dreadful; as more victims are raped and gored, blood upon blood, the crowd intone a drugged and ecstatic chorale brutally shattered by a screeching chorus of winged furies. Here the music's crazy momentum displays Birtwistle's talents at magnificently full stretch.

And also the talents of that great Wagnerian bass-baritone John Tomlinson, whose infinitely sorrowing tone and well observed movement bring this beast to convincing life. When he dreams, he enters a dialogue with his sepulchrally amplified mirror-image: again, the whole drama is transported onto another plane. If we must leave that plane once more for some wordy to-and-fro between Theseus and Ariadne, the evening is saved by two further fantastical excursions: to an extraordinary oracle - countertenor Andrew Watts with big womanly breasts – and to the monster's pathetic, all too human demise.

Thanks to a superb cast and impeccable playing under Antonio Pappano, the evening is a glittering success. But what Birtwistle has done is give us one opera inside another. The outer one is strident and earthbound; the inner one – ending with the Minotaur's Caliban-like dying aria – burns with visionary fire.