I hadn’t been planning to write this week about the Royal Opera’s first complete Les Troyens for 40 years – over the coming months much will be written about this production and the live transmissions and DVD that will come of it, not to mention its outing at the Proms – but it turned out to be one of those Covent Garden nights that is so overwhelming it seems to demand immediate reaction, following on as it did from a shocker two nights earlier.

I’ve experienced many amazing Covent Garden nights – Solti’s 1963 Figaro with Geraint Evans, Freni, Berganza, Ligabue and Gobbi as a matchless Almaviva; the following year’s unbelievable Otello, Gobbi again, with the American tenor James McCracken; Birgit Nilsson spellbinding as Elektra and Salome, leaving one open-mouthed in unbelieving awe; Rudolf Nureyev in the pas de deux from Le Corsaire with Margot Fonteyn; an unheralded young tenor by the name of Pavarotti with some rather special top Cs in La Fille du Régiment – and Colin Davis’s Les Troyens from 1969, with Jon Vickers as Aeneas, Josephine Veasey as Cassandra and the wonderful Janet Baker as Dido. More recently, Elīna Garanča’s searing, sexy Carmen; and (now we enter controversial territory) Angela Gheorghiu – with Terfel in a Tosca where the second act encounter almost matched that of the legendary Callas and Gobbi themselves - as Violetta; and, as many would see it, portraying herself in a sparkling Adriana Lecouvreur.

You can see, then, that I am not one of Gheorghiu’s detractors. So Saturday night’s La Bohème was a major disappointment. Bohème is one of those shows (Traviata is another) that Covent Garden puts on rather a lot, reliable seat-fillers with ever-changing casts. But this was different. Twenty years ago the Romanian had made her Covent Garden debut as Mimi, singing opposite Roberto Alagna as Rodolfo. A tempestuous relationship followed: the couple married, rowed, separated, swore never to sing together again. Then reconciliation and now we were promised (just) two performances with the happy couple back together again.

Gheorghiu still looks good on stage but Mimi is not an ideal role for a worldly-wise, knowing-all diva. The Mimi who knocked on Rodolfo’s door was lacking any pretence of innocence, rather the accomplished seductress conspiring with the audience with what felt like knowing winks. Meanwhile Alagna cherished his every top note, leaving stand-in conductor Jacques Lacombe hanging on to his baton for seemingly endless longueurs while the tenor savoured his moments: time to pop out for a quick one. I’m sorry I didn’t see Joseph Calleja’s performances – he is a class act and I’ve heard only good things about his Rodolfo. But this was Covent Garden with the Stars, with musical and dramatic integrity sacrificed for big names. The audience loved it. Wild applause. It’s what Covent Garden does. Fortunately not very often – and two nights later Les Troyens has restored my faith.

With serious reservations about aspects of the production, this new realisation of Berlioz’s greatest achievement – always a major event given the size of the forces required and the rarity of its performance – joins that litany of the great Covent Garden nights. I have never experienced the chorus in finer voice, the orchestra (as so often) on fire for Antonio Pappano, a production which I loved for the first three acts and was content with for the fourth (the long mandatory ballet sequence before Dido’s and Aeneas’s great love duet not as riveting as much of the earlier action). Les Troyens comes in two distinct parts: the first two acts comprise the tale of the Trojan Horse and the fall of Troy, taken principally from Book II of Virgil’s Aeneid. The remaining three acts, dealing with the Trojans in Carthage and the love affair between Aeneas and Dido, are drawn from Books I and IV.

While Aeneas himself bestrides the whole work, part one revolves around the ignored warnings of the Trojan princess and prophetess Cassandra, a riveting Anna Caterina Antonacci stalking the stage and dominating proceedings with a furious intensity that will live in the memory. I have never seen the Italian soprano in such fine voice and she was matched by Bryan Hymel’s glorious Aeneas. A relatively late replacement for Jonas Kaufmann, the lower-profile American tenor had a lot to live up to, though the portents were promising – he was the Prince in the much derided but musically spellbinding Rusalka earlier in the season. We will be hearing a lot more of Hymel – he put me in mind of Vickers, his predecessor in the role – and he carried the mantle of the Trojan hero with aplomb. David McVicar’s production and Es Devlin’s elaborate sets matched the scale of the epic tale, the chorus filling the house with an intensity that rings in my ears still as I write this.

The handsome set for the opening of the Trojans at Carthage was another delight. I remember Eva-Maria Westbroek most vividly as the depraved Anna Nicole in the premiere of Mark-Anthony Turnage’s opera last year. The Dutch soprano was in her element there and here she was portraying a Queen who also goes off the edge when her lover answers the call of destiny and the gods, and deserts her to found a new empire in Italy. Everything was going so well up to that point. In this production, too. Suddenly, though, as Berlioz’s music builds to its long dramatic climax (the curses of a woman spurned being hurled down on Aeneas and the Trojans, Dido’s prophesy of a great Carthaginian hero, Hannibal, who will avenge her and destroy the Roman empire), it seemed like someone had run out of time or money and Westbroek was left singing some of Berlioz’s most splendid music in front of a curtain while a lengthy set change was going on behind. This was not helpful: Antonacci’s Cassandra was all in context. Suddenly Westbroek’s Dido seemed more like a soprano giving a recital. When we finally saw the pyre on which Dido would burn every memory of Aeneas and their love it was strangely lacking the epic scale of all that had gone before. A strangely low-key ending to what was, in the main, one of the most remarkably exhilarating Covent Garden evenings for quite a while.

Les Troyens is a co-production with the Vienna State Opera, Teatro alla Scala, Milan and the San Francisco Opera. It will be released worldwide into cinemas in November. The performance on July 5 will be streamed live at thespace.org and The Space channel (Freeview HD channel 117) and will be available for repeat viewing online until October 31. The July 5 performance will also be broadcast live on French television.