A single magpie settles on a branch beside a lake. Two boys stalk through the long reeds. The older one hands the younger, fair-haired lad a slingshot and watches as he takes aim, aghast when the stone hits its mark and the magpie thuds to the ground. Using video projections in his new Glyndebourne production, Claus Guth fleshes out the backstory between Tito and Sesto, so we understand the sovereign’s inevitable act of forgiveness – the opera’s title La clemenza di Tito rather gives away the denouement – when the emperor spares Sesto’s life after surviving an assassination attempt.

It was obviously a complicated relationship, confused by scenes in which the young Sesto appeared to be drowning. In Act 2, when Sesto appeals to Tito for forgiveness in “Deh per questo istante solo”, the child actors step down from the screen to haunt their adult selves, triggering memories. These projections – subject to a few gremlins during the overture – display on a black box beneath which the action takes place amid wild grasslands reminiscent of those youthful memories.

The black scrim rises to reveal the upper half of Christian Schmidt’s split level set, a grimly lit office from which Tito rules his empire. Here, in this cold, contemporary setting, Tito is less political leader, more chief executive heading a besuited chorus of lackeys. The stage allows Guth to demonstrate Tito’s sense of isloation – a loneliness increased by also depicting the departure of Berenice (the one woman he truly loves?), a match destined to fail for political reasons. Where Guth’s updating doesn’t work is in the desperate need for Tito to take a wife in the first place, whether Berenice, Sesto’s sister, Servilia, or Vitellia, the most questionable of the three given her father was usurped by Tito’s father and who is bent on vengeance. Guth keeps Mozart’s taut opera seria on the move though, with convincing direction of his singers.

Robin Ticciati conducted the Orchestra of the Age of Englightenment with plenty of punch and period instrument tang. The fortepiano and cello continuo pairing of Ashok Gupta and Luise Buchberger were raised in the pit, able to see the stage and react to the singers. The pick was Anna Stéphany who sang a terrific Sesto, mellifluous and fluidly phrased, with plenty of agility in the busy ornamentation of “Parto, parto” (aided by the burnt caramel tones of Antony Pay’s basset horn obbligato). She was a believable figure, torn between loyalty to his childhood pal and his love for Vitellia, who is keen to use him as a tool for revenge.

Stéphany and Michèle Losier (a splendid Annio) share silvery timbres, but mezzo contrast came in the form of the coppery tones of Alice Coote as the power-hungry Vitellia. This was a strikingly vivid interpretation capturing Vitellia’s fickle, grasping nature, Coote vamping it up in a “Non più di fiori” presented as a mad scene with the house lights up. The role either requires a soprano with exceptional low notes or a mezzo with an exceptional top and here Coote fell short, despite throwing her entire vocal armoury at it. From soft mezza-voce to booming Wagnerian, hers was a mannered but dramatic, raw reading that won’t be to all tastes. Joélle Harvey was an angelic-voiced Servilia while Clive Bayley’s vinegary bass suited Publio, presented as a sinister Big Brother figure at the centre of the political web. The excellent Glyndebourne Chorus was subjected to a certain amount of Peter Sellars-type armography.

Richard Croft, a late replacement for Steve Davislim who left the production due to “artistic differences” has a supple tenor, but occasionally struggled to project vocally from his black box empire, his top notes short and dry. Tito was commissioned to celebrate the coronation of Leopold II as King of Bohemia, so Mozart’s hands were tied to presenting the ruler in a benelovent light. Croft presented a Pilate like figure, washing his hands at one point, before suffering a moving breakdown, scything the reedbeds before cradling them in his arms. Croft employed daring pauses in recitative and delivered a truly moving, noble “Se all impero” as Tito decides he does not desire “loyalty that is secured by fear”.

After making his decision to eventually spare Sesto, Tito symbolically removes his jacket while a magpie soars to the skies. Does Guth believe in happy endings though? The manipulative Publio dons a jacket to wrest control, toasted by the suits. One senses darkness continues to reign.