‘Goodness Triumphant’ is the subtitle of Rossini’s La Cenerentola, and you’d better believe he delivers. It’s the sweetest thing imaginable; true, the stepsisters are awful, but their spite bubbles over in streams of such sunny major-key effervescence that it’s hard to hold it against them. As for their father Don Magnifico, you can’t seriously hiss a villain whose principal ambition is unhindered access to the palace wine cellar. It’s testimony to just how deftly Rossini handles his material that the final scene – in which the now-royal Cinderella asks only that her stepfather address her, for the first time, as ‘daughter’ – can still make you go as gooey as a chocolate fondant.

Perfect summer opera fare, then, and a shrewd choice for a company that has to play it safer than most. Country-house opera festivals are a warm-weather species. Nevill Holt Opera, in Leicestershire, is the most northerly major outpost, and even that’s now in doubt. In March this year they cancelled one of their two planned productions (insufficient ticket sales, apparently), and shortly afterwards their artistic director resigned. Yet they have a gorgeous location and probably the best small opera theatre of any of these festivals. Plus, right by the door, they’ve got the ‘Ed Stone’: the ill-fated Miliband monolith from the 2015 election campaign, subsequently acquired by Nevill Holt’s owners for the lulz. Instant comedy before you’ve even taken your seat.

This Cenerentola was a little delight: a cheerful staging from Owen Horsley (the designer was Simon Wells) that updated the fairy tale to a bubblegum 1960s, with a boogying male chorus kitted out like the Beatles in drainpipes and mop tops. Horsley gave his mostly youthful cast (another Nevill Holt strength) ample space to bring their characters to life, and they ran with it: whirling through Rossini’s dizzying patter songs and supercharged coloratura with easy charm and an irrepressible sense of enjoyment.

So the stepsisters (Lorena Paz Nieto and Nancy Holt) sulked and pouted in nylon negligées. As Prince Ramiro, Aaron Godfrey-Mayes’s elegant tenor was amusingly at odds with his Michael Fabricant hairpiece. Grace Durham, in the title role, was entirely endearing; her expressive eyes and sad little sighs complemented singing that pulled off the unlikely feat of being both tender and brilliant. Trevor Eliot Bowes tiptoed dandyishly around as Alidoro, with a depth to his voice that – once again – made a droll contrast with his feline aura. And Grant Doyle anchored the whole team as a Don Magnifico whose well-oaked baritone and faintly goofy stage presence generated a genial glow where a more cynical director might have injected a sting.

Mission accomplished, then? Producing an evening of featherweight, brilliantly achieved fun is as high an artistic challenge as anything in theatre, and thanks to an imaginative director, an engaging cast, and the Royal Northern Sinfonia under Dionysis Grammenos (spooling out solo after exquisitely turned woodwind solo), Nevill Holt brought it off. It’d be rash to draw premature conclusions – we don’t get to see the balance sheets – but going on artistic merit alone, Nevill Holt Opera deserves to be around next summer. Let’s hope it is.

At Covent Garden, meanwhile, the prospect of a late-season Verdi revival is usually about as appetising as carvery leftovers. But this was Don Carlo, an opera so mighty that any halfway-decent staging elevates everyone involved. The production was Nicholas Hytner’s, from 2008 (grand, gloomy and sublime), and the selling point was Lise Davidsen as Elizabeth. She was magnificent: singing with a voice that could slice like a blade or open out, as if catching the light, to blaze high above the smouldering brass and roiling ensembles (Bertrand de Billy conducted a performance of nagging, juddering momentum; opening sepulchral depths beneath Verdi’s orchestra).

Elizabeth’s pathos was there, too, as well as her royal pride. The pain in Davidsen’s eyes as she was dragged away from Carlos (an open wound of a performance from Brian Jagde) prefigured the anguish in the face of her husband Philip II (John Relyea) three acts later, as he cradles the woman he knows has never loved him. In his scene with the Grand Inquisitor (a reptilian Taras Shtonda) Relyea’s Philip – the fire-and-sword tyrant of Act Three – collapses, imperceptibly, into a broken, hollow-eyed wreck.

At moments like this, Don Carlo is up there with Der Ring des Nibelungen as a study of power and the human soul: the Marquis of Posa plays his hand with courage and compassion (mirrored in Luca Micheletti’s taut, ardent performance) and is destroyed with the rest. Like King Lear, this is a drama in which no serious artist can bring anything less than their A game, and that was the case here. By Act Five, the Covent Garden audience felt ready to explode; and for once, I was entirely with them.