Un ballo in maschera, Opera Holland Park, London

The last thing you need is a voiceless tenor on opening night of Verdi's troubled political thriller Un Ballo in Maschera. The pivotal role of Gustavus III, assassinated at a masked ball in the Royal Opera House, Stockholm, in 1792, has been much beloved of big stars throughout its chequered history. Rafael Rojas is hardly that but David Rendall has been and together they rescued a near-disaster, Rendall singing from the pit, Rojas moving and mouthing furiously on stage.

Director Martin Lloyd-Evans, meanwhile, had his cake and ate it, opting in part for the Boston revision of the opera (one of many adjustments prompted by Verdi's run-ins with the Italian censors) but with one significant promotion: King Gustavo was no longer merely the colonial governor of Massachusetts at the time of the War of Independence but President of the United States in the here and now. That ticked a number of boxes, not least his supreme power and the looming spectre of assassination – but it also left the director open to the wrath of the traditionalists, one or two of whom booed vigorously at his curtain call.

But this is opera, and turning the fortune-teller Ulrica into a kind of Mystic Meg (Carole Wilson, alarming in sequins with chest notes to match) bellowing her fateful prophesies amid clouds of dry ice while taking the odd important call on her mobile is no less credible than the original text – and actually when she advises Amelia to seek out the "place of death" there to find the "drug" that will rid her of her passion for Gustavo, the lawless, gun-toting ghetto rings frighteningly true. But the self-administered shot of Big H during Amelia's big number? No wonder her lover was opening his mouth and making no sound.

On that score, David Rendall's voicing of Rafael Rojas was adequate, top notes in place but so much else threadbare now. Olafur Sigurdarson's Renato was all bluster and no legato. Which gave the stage to the young lady everyone is talking about – Amanda Echalaz. It's rare to find a voice of such true spinto colour, dark and plangent with a stonking top C where, as here, required. Echalaz just needs to find more quiet dynamics and that facility for taking the voice away to a state of weightlessness above the stave. But my goodness, she's exciting. Let's hope the right people are nursing this exceptional talent. She's almost ready to fly.

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