It's a mature but little known work, though one duet was used in the film of A Room With a View and the second act chorus in a Paris dance hall is a magnificent, much-loved and swirling set piece.
Tom Hawkes' superb production and Kate Ladner's stellar performance as Magda, "la rondine" or swallow, who flies away at the end of summer (thus protecting her true love's family honour from her own besmirched reputation as a "kept" woman), laid out a third act of breathtaking beauty and melodic subtlety as the dilemma unravels on the terrace of a seaside hotel.
The whole experience was curiously enhanced by the extraneous sounds of peacocks cawing, dogs barking and small children shouting, not to mention a gale force wind blowing through the tented auditorium with Biblical ferocity.
Producer James Clutton and general manager Michael Volpe have created a west London festival that is one of the city's cultural magnets. And not just for musical theatre lovers. Every time I go near Holland Park I seem to bump into newspaper executive Rod Gilchrist jogging in access-all-areas mode.
En route to La rondine, we bantered briefly about the phone hacking scandal: "Fair cop, guv", "See you in court," that kind of thing... but it was still only 6pm, a full hour and a half before the head of the Metropolitan Police announced his shock resignation.
Every time you go inside a theatre these days you wonder what new dramatic twist awaits you on the other side. Not that any of this dampened the holiday mood inside the picnic area.
For the first time, we took advantage of the tables for hire at the side of the auditorium and tucked into our bagels, sausages and warming red wine with a mounting sense of musical pleasures ahead: much easier, and more convenient, than scrabbling with cutlery and paper plates on the lawns at Glyndebourne.
There was even a hint of country house hedonism at the poky King's Head on Saturday night, when another (much smaller) full house packed in to see Mark Ravenhill's erotically recharged and jazzily reconfigured version of Monteverdi's The Coronation of Poppea.
More than a few punters were decked out in their summer finery, and one party arrived with bottles of booze and party nibbles. The whole occasion, in fact, starting with the production itself, was a spirited subversion of operatic etiquette, although this did not discourage the odd "brava" from invading the rapturous applause at the end.
This version of Monteverdi's masterpiece could not be more different from the brilliant "trad" baroque Italianate production for ENO by the late Steven Pimlott, which more or less catapulted Anna Coote to stardom. Ravenhill and musical director Alex Silverman have cut minor characters and deities, as well as most of the choruses. They also make Monteverdi sound like a jazz re-write of Monty Python, re-jigging the score for piano, double bass and soprano sax and injecting some raucous humour into the cross-dressing shenanigans of the murder plot.
It's absolutely brilliant. Not only that, OperaUpClose have re-arranged the King's Head for the first time as a traverse theatre, making maximum use of the space and setting the action around Seneca's blood bath and in front of a full length mirror where characters either preen sumptuously or question tentatively their reason for living.
The debauched emperor Nero and his concubine Poppea are both sung as sopranos and played as full-on Sapphic sisters by the crop-haired Jessica Walker and the wonderfully buxom and sensual Zoe Bonner. David Sheppard's sensitive alto Ottone is more of a delicate counter-tenor, while Martin Nelson as Seneca holds a steady bass line as he slits his wrists and the water changes colour like the shower in Psycho.
Aren't stage effects amazing? The water turns red, but as all the characters slop in and out of the sunken bath, none of the dye seems to come off on their feet or clothes. We pondered this almost as deeply as the ingenious rediscovery of Monteverdi's music as modern jazz.
A fond farewell to that magnificent Australian actress Googie Withers, who once asked John Gielgud why he never cast her in his productions. "Because of your stupid name," he allegedly replied. "Who's Googie Withers?" Danny La Rue used to ask in his cabaret act, before providing his own answer: "Everyone's, in cold weather."