“Here be dragons!” warned seafaring maps of yore, denoting uncharted territories. Martin Kušej, undertaking his first Royal Opera exploration, excised the sea monster from his vision of Mozart’s Idomeneo. Well, there was a baffling appearance from a rubber shark, but we’ll file that under ‘Red Herring’. For Kušej, the monster takes on another, more relevant, more believable form: a brutal regime. Kušej’s is a thoughtful, intelligent production – challenging, but nowhere near as provocative as his Josef Fritzl inspired Rusalka or his asylum-seeking Flying Dutchman.

Annette Murschetz’s set is a rotating series of walls and doorways, sometimes giving the impression of a labyrinth. A tyrannical leader, Idomeneo, is caught in a post-war power struggle with his more benevolent son. We see Idomeneo’s troops beating the Trojan prisoners, forcing them to rejoice at gunpoint to mark Idomeneo’s return. Choking fumes swirl around the corridors at one stage, suggestive of gas chambers or the incineration of bodies. With Kušej, there is no demand from Neptune to sacrifice the first living creature Idomeneo should meet on his return to Crete. Egged on by the High Priest, it’s merely a pretence so he can dispatch Idamante, his political enemy. Ilia spurs on Idamante’s loyalists to rebel. Idomeneo is ousted from power and – seemingly blinded – pathetically offers his abdication speech to an empty stage.

Following the final chorus, Mozart’s ballet music is retained (against the director's will, as could be discerned from a Times interview last week) but Kušej presents a series of frozen tableaux suggesting that the newlyweds Idamante and Ilia already have blood on their hands and the whole cycle of despotism will be repeated.

There are some directorial quirks which passed me by: the shark; the plastic fish wafted around by the chorus as the ‘monster’ is sighted at the end of Act II; and Arbace as a homeless busker, armed with an accordion (mercifully tacet). But on the whole, Kušej’s approach is intriguing and it didn’t warrant the angry, vociferous response it received at the curtain call. And it’s backed up by some excellent musical performances.

Initially, Matthew Polenzani seemed too nice to be a tyrant. With his honeyed tenor and gentle stage presence, he started out as a sympathetic figure, but he grew into the role, nailing “Fuor del mar” splendidly. The odd casting of the night was Franco Fagioli’s Royal Opera debut as Idamante, originally a castrato role, but later rewritten for tenor and now usually sung by a mezzo-soprano. This was my first experience of hearing the Argentinian Fagioli live and his is a remarkable voice; a very high countertenor, but without cloying soprano sweetness, he projects strongly and has amazing agility.

Sophie Bevan sang Ilia with passion and grace, her silky soprano charming at every turn, particularly in her Act III aria “Zeffiretti lusinghieri”. Malin Byström was a feisty Elettra, the daughter of Agamemnon and Ilia’s rival for Idamante’s attentions. Her upper register can sound pinched and her lower notes are occasionally breathy, but Byström’s attack in her ‘rage’ aria “D’Oreste, d’Aiace” was entirely admirable. The musical highlight of the evening – and of Mozart’s entire score – was the quartet “Andrò ramingo e solo”, Bevan, Byström, Polenzani and Fagioli all on their finest form. Stanislas de Barbeyrac, another house debutant, displayed a welcome heroic tenor quality, even if his character never felt fully explored.

Also making his Royal Opera debut, Marc Minkowski drew some remarkably ‘historically informed’ playing from the resident orchestra. Hard timpani sticks, incisive, braying brass and splendid fortepiano continuo (Francesco Corti) contributed to a tangy sound. For Ilia’s aria “Se il padre perdei”, Minkowski shuffled his pack to allow solo flute, oboe, bassoon and horn to stand together to provide obbligato support. Tempi were brisk, Minkowski often dancing on the podium. Once or twice, orchestra and chorus parted company, but this was an exciting (long overdue) debut.

Idomeneo holds few claims as anyone’s favourite Mozart. As an opera seria, it can suffer from the accusation of “too many notes” that Emperor Joseph II hurled at Die Entfuhrung aus dem Serail. Yet under Kušej’s direction, and with Acts I and II welded together for a very long first half, the action sped along. His approach to the opera made much dramatic sense, even if that approach didn’t meet with universal acclaim. Perhaps in Kušej, sections of the audience eventually found their monster.