I Pagliacci, Royal Opera House, London

A clown prince worth waiting for

Well, the donkey stole it. He had done his walk-on part, but he wasn't going to be fobbed off, let alone upstaged, by the likes of Placido Domingo and Angela Gheorghiu. There was a riveting moment when Gheorghiu's hapless Nedda, poised to perish in a very nasty bit of marital brouhaha, launched into her wafting Act I love duet with her lover, Silvio (the Siberian Dmitri Hvorostovsky, bringing a stunning lieder-like quality to this minor role). And that was when our four-legged friend decided to join in.

Maybe one of the well-acted, tiny, impoverished street kids in this busy Franco Zeffirelli production had tugged on his tail. Maybe one of the terrific commedia dell'arte clowns or the fat lady (she didn't sing, but, as Columbine, she played stooge to Gheorghiu's Act II twitterings) trod on his hoof. Anyway, that was it. He hee-ed and he hawed. Quite some instrument, that.

Which only goes to show: don't put your donkey on the stage, Mrs Worthington.

It was a visually entertaining show that didn't really come good until the end. In Act I, Zeffirelli, doyen of Italian opera-cum-film directors, who designed as well as directed here, saturated the stage with sprawling Italianate tenements that merged the shady prowlings of Robert De Niro in Taxi Driver or The Godfather: Part II with much Fellini-style urban freneticism from Terry Edwards's jam-packed (but musically thrilling) chorus.

Not much room was left on board ship for good old Placido, who appeared, tumbril-borne, rear-stage. From the outset he sounded thin and looked willowy and rather silly in his white gear. Only when he got his clown outfit sticky and the make-up dripping, one and a half hours into the show, did the great man's Canio come anywhere close to his equally distinguished understudy, our own home-grown boyo Dennis O'Neill, who will be singing the role on the evenings, when the indefatigable Domingo, after clowning on stage in the afternoon, gamely takes his turn in the pit with the baton.

Last night's conductor, assuming the mantle of Arturo Toscanini (who conducted the premiere), was Antonio Pappano, the Royal Opera House's vital music director, serving up wonderful, dark sounds - those cellos and basses especially. Gheorghiu's "bird" aria was exquisite, and her clowning, complete with lashings of spaghetti, wittily refined. But for all the cheerful high jinks, the fire-eaters and unicyclists, the cheerful transvestites, carabinieri and confetti, and despite the evening's best arias - arguably not Domingo's, but Hvorostovsky's and Beppe's (the impressive young St Petersburg tenor Daniil Shtoda, as Harlequin) - it was the ending that counted.

Ruggero Leoncavallo's Pagliacci builds, inexorably, towards its bloody climax (the Georgian baritone Lado Ataneli's nasty, robustly sung Tonio splices the fatal knife into Domingo's hand) with the grim inevitability of Hamlet or Oedipus Rex. Indeed, Leoncavallo, the very epitome of Italian verismo, composed an Oedipus opera himself, and you can see why.

Domingo himself really needs to play King Lear. His best touch in Act I was his face: subtly shifting contours that fused distaste and contempt, anxiety and fear, pain and threat. Both his arias were a mite too set-piecey, and none too well acted. But at the end, just for five minutes, murder and all, he gave us the full works. And I guess that's what you go for.

To 20 July (020-7304 4000)