Like the bold scheme for liberating the Flemish masses planned by the excitable Don Carlo and his steadfast chum Rodrigo, the Royal Opera's new production of Verdi's epic political tragedy starts well, then somehow fizzles out.

After two acts, with Nicholas Hytner's staging unfolding this Habsburg power-struggle so cogently in Bob Crowley's handsome, uncluttered period sets, I thought this might be one of the great nights in the theatre. But after five acts (for Covent Garden has opted for Verdi's five-act 1886 revision in Italian) I could hardly wait for Robert Lloyd's baleful ghost of Charles V to come and put Rolando Villazón's broken Carlo out of his misery.

What goes wrong? Very obviously, two of the central characters.

Villazón and his adored Elizabeth, Marina Poplavskaya, perform stunningly in their heartstopping Act I meeting, where they find instant mutual love in a magical, silver-tinted Fontainebleau. They have chemistry, ardour, spirit, sensuality.

That, however, turns out to be the zenith of their evening.

Villazón certainly radiates the aura of unstable volatility that Carlo needs, but his grainy voice sounds more and more pressurised. And as Poplavskaya tires in Acts IV and V, her tuning problems and threadbare top register aren't pretty to hear. The role is beyond her at present, as the Royal Opera hierarchy should have realised.

But Hytner's production must also shoulder some blame. He elicits wonderfully assured acting in intimate scenes. You can really feel the shuddering clash of ideologies, for example, when Ferruccio Furlanetto's brooding, sinister and repressive Philip II confronts Simon Keenlyside's magnificently forthright, clean-cut Rodrigo - “the only true man in this swarm of humanity”, as Philip rightly says. Or when Philip finds himself, doubtless to his surprise, speaking up for idealism and kindness in his verbal punch-up with Eric Halfvarson's splendidly grotesque, palsied Grand Inquisitor. Or when Sonia Ganassi's forceful Eboli is bewailing her own treachery in a hail of knockout top notes.

Yet as the opera progresses, and the chorus - the mob - should increasingly make their disruptive presence felt, Hytner's staging seems bland and tokenistic. The sudden, lurid lighting of the burning heretics at the end of auto-da-fé scene is more akin to one of those comically gruesome waxworks in the London Dungeon than convincing theatre. And there's no sense of menace or impending anarchy about the mob's intrusion in the last act. They seem a docile bunch.

That's a pity, because one longs for the stage action to match the intensity of what Antonio Pappano delivers in the pit. The orchestral playing is superb, from the offstage hunting horns at the opening and the beautifully gauged ebb and flow of the love music to the sepulchral creepiness of the slithery sounds conjured up for the Grand Inquisitor.

Not for the first time, Pappano delivers a Verdi masterclass. That's worth catching on Radio 3 on June 28.

Box office: 020-7304 4000

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