All Savoyards, whether conservative or liberal towards productions, have been grievously practised upon. They told us to expect the first professional London grappling with Gilbert and Sullivan’s eighth and, subject-wise, most problematic operetta in 20 years (23, if the reference is to Ken Russell’s unmitigated mess, one of English National Opera’s biggest disasters). Yet this is not Princess Ida as the pair would recognize it.

Johann Christian Bach’s Amadis de Gaule, which is receiving its first London run this week in a vivid and charming production at University College London Opera this week, suffered like many a talented work from the blinkered whims of musical fashion. History has generally focused on more pressing issues in late 18th-century Paris than the operatic rivalry between the schools of Gluck and Piccinni, but Bach’s failure to please either faction along with the minor disturbances of 1789 has, it’s believed, caused the subsequent neglect of this poignant and sensuous piece.

If you’re looking for rare festival Handel, better a pasticcio – take that as shorthand for a cut-and-paste job mostly from previous hits – than one of those original operas in which the composer only goes through the motions (and I’ve heard a few). Call in a reasonably cutting-edge director, make sure you have a motivator of the calibre of Laurence Cummings in the pit – not difficult in this instance, since he’s the devoted force behind the London Handel Festival – and find the brightest and best of young singers.

When is a famous aria more than just a showpiece? When it’s a narrative of a future event conjured by a hope beyond reason, which is what Madama Butterfly’s “Un bel dì” (“One fine day”) ought to be but so rarely is: too often prima donna overkill and stereotyped mannerisms get in the way. Not with Latvian soprano Kristine Opolais. Her Butterfly’s gestures can be stylised but always unusual, setting her apart, an ex-dancing geisha driven almost mad in a three-year wait for a “husband” who won’t come back. The effort of will sees her crumple in the aftermath of her vision.

“Do you think they’ve got enough plot to get us through to the end?” I overheard a lady anxiously asking her husband during the interval. It was a fair question. Donizetti’s The Wild Man of the West Indies was written within a year of L’elisir d’amore, and the two operas share many things, but not that spark of genius that can transform a pantomime into a drama. Rarely has so little happened in an opera, and with even less effect.

"No heckling. No smoking. No making love," read the nifty video projections announcing the rise of the new Mahagonny at the Royal Opera House. Why so coy? Could they not give us a bang for our buck, or even a slow comfortable screw?

The Southbank Centre’s Women of the World Festival may have been the largest cultural event marking International Women’s Day 2015, but it wasn’t the most ambitious. Over at the Barbican two women were responsible for a multimedia opera staging whose spectacle, level of detail and sheer force of personnel involved was staggering.

How can a feisty village dame duetting “lackaday”s with the mounted head of a long-lost, nay, long-dead love be so deuced affecting? Ascribe it partly to the carefully-applied sentiment of Gilbert and Sullivan, slipping in a very singular 11-o’clock number after so much Gothick spoofery, partly to two consummate and subtle singing actors, Amy J Payne and John Savournin, in a production of spare ingenuity by the latter, true Renaissance/Victorian man equally at home in opera and operetta.

Now that opera houses mostly lack either the will or the funds to stage the more fantastical/exotic pageants among 19^th century operas – the Royal Opera production of Meyerbeer’s mostly third-rate Robert le Diable was an unhappy exception – it’s left to valiant concert-performance companies like Chelsea Opera Group to try and trail clouds of kitschy glory. Which, thanks to the usual astute casting of world-class voices for the solo roles and a remarkable semi-professional orchestra under Royal Opera chorus master Renato Balsadonna, they did last night.

Mozart’s The Magic Flute is one of those operas, like Verdi’s Il trovatore and all the mature Wagner masterpieces, which need a line-up of equally fine singers but rarely get it in the compromised world of the opera house. With Christiane Karg and Pavol Breslik as the trial-enduring lovers joining three performances in the latest revival of David McVicar’s production, and only Anna Siminska’s fifth-element Queen of the Night unknown to me, last night's team looked good in principle.