They have to work hard, those warhorses. The Toscas, the Bohèmes, the Traviatas: these are the staple works upon which any major international opera house relies in order to cross-subsidise occasional productions of more unusual repertory. Franco Zeffirelli’s much-loved Tosca for Covent Garden, created for Maria Callas, achieved four decades of long service, while Jonathan Kent’s reassuringly traditional replacement has lasted almost 20 years. High stakes, then, for Oliver Mears, the Royal Opera’s Director of Opera, in deciding what the Tosca for our age should look like. How this unflinching production will fare in umpteen long runs to draw in the tourist crowd remains to be seen, but in its current incarnation, with a trio of star leads, it is a sensation.

Act One’s marble, debris-filled church, wooden benches upended, is not so different from many another modern Tosca, but the second and third acts are novel indeed. Act Two – the most effective of the three – takes place in a vast marbled room, with enormous gold doors in front of which the singers look the size of dolls. Bar a couple of office chairs, the only item of ‘furniture’ is a low marble block, which triples up as a dining table, a casting couch (as it were), and a slab for a corpse. There is something of the aesthetic of Albert Speer or of Marcello Piacentini, Mussolini’s architect in chief, in this aggressive plainness and sense of epic scale. And then, in contrast, the third act contracts, the action taking place in a claustrophobic box within a box. The walls of this small, tiled cell, a shower hose fitted at one side, are at once wipe-cleanable and sordid with grime and a previous occupant’s blood. The stage business that is enacted as the bells of Rome gently toll – usually a moment of utmost serenity – requires a strong stomach. The 14+ age rating is to be taken seriously.

When are these events taking place and where? Here, Mears refuses to be pinned down. The bombed-out church has led some critics to conclude that Act One must be set towards the end of the Second World War, but this is surely a misreading. Tosca’s dark pink cocktail dress in Act One suggests somewhere around 1960, though it could equally be from the 1980s or beyond, as could the frumpy jeans and knee-length skirts of the female chorus. Scarpia’s double-breasted suit, bad hair and outsize spectacles also point to the later 20th century. The set for Act Two evokes the 1930s or the 1970s, but simultaneously has something of the aesthetic of a contemporary billionaire’s mansion. If we are in a more recent era, perhaps even the present day, it is hard to see why Rome is being bombed, masonry falling from the ceiling as congregation members cower during the climax to the Te Deum. But it is far from certain (inescapable references in the libretto aside) that we are actually in Rome at all. There are decided shades of Eastern Europe here, even, perhaps, of Russia.

Which brings us to the opera’s leading lady. Mired in controversy outside the opera house for being insufficiently critical of Putin, Anna Netrebko electrifies the audience inside it. All rumours of vocal decline are misplaced: she appears to be at the height of her powers, the chest voice opulent and fearsomely powerful, the top notes as secure and lithe as you could wish for, each note of her ‘Vissi d’arte’ pulsating with emotion. It’s a breathtaking comeback.

The whole performance seems as easy for Netrebko as clicking her fingers and this sense of ease pervades her scenes with the impressive young British tenor Freddie De Tommaso. Often, Tosca and Cavaradossi fail to convince as a couple: bickering from the moment we meet them, they seem to lack the heartfelt romance of Mimì and Rodolfo, or the sexual attraction of Manon and Des Grieux. But Netrebko and De Tommaso, relaxed in each other’s company and well-matched in vocal weight and tone, approach the relationship with an entirely naturalistic, spontaneous playfulness. I have never heard so much affectionate laughter from an audience in a first act of Tosca, and there is yet more for Alessandro Corbelli, the great Italian comic baritone, as the Sacristan (truly a piece of luxurious casting in a minor role).

In many Toscas, the best you can hope for, principals-wise, is two hits and a miss. Often we are given ‘the Tosca and Scarpia show’, with a rather disengaged star tenor who is there purely for his two big arias, or a convincing pair of lovers and a Scarpia who is a stock pantomime villain. There is none of that here. Gerald Finley (physically almost unrecognisable) is a sleazy office boss surrounded by sinister acolytes, who watches CCTV footage of his torture room while eating a greasy takeaway from a foil box. His confrontation with Tosca is as thrilling as you could hope for, his singing exquisite in the ardent music where Scarpia tries to convince the singer that his lust is something more sincere. Again, the acting between the pair is completely naturalistic, Netrebko the epitome of sassiness as she retorts ‘Non so nulla!’ during the torture scene, rising to all-conquering diva as she slams her bouquet down on to the face of her crushed tormentor. No respectful arrangement of candles for this Scarpia; in fact, the one candle in the room is used as a blunt instrument.

And then Act Three, with its conveyor belt of executions, is hands-over-eyes horrific. We are not used to seeing Toscas that are as stark, as chilling, as graphic, as this. In sugar-coating nothing, perhaps Mears gets to the real heart of the piece; he takes the opera out of its cosy familiarity and gives us an insight into the shock audiences must have felt when first watching it in 1900. With its outstanding cast, and sharp, detailed conducting from new Music Director Jakub Hrůša, this feels like a historic night in the theatre. And yes, a certain meta-narrative is irresistible as we watch a fictional diva struggle to escape from the all-pervading sway of a powerful tyrant.

Tosca is at the Royal Ballet and Opera until 7 October