A rare Handel opera, played by Laurence Cummings and the London Handel Orchestra, long the specialists of such music, sung and acted by a young, energetic cast clad in costumes of pure eye candy, in what are now the very pleasant surroundings of the Royal Opera House's Linbury Theatre. What’s not to like?

In point of fact, last night’s performance had two Achilles heels – giant, life-threatening ones, easy targets for any passing Trojan archer. But before coming on to those, let’s consider the evening’s many positives.

Alessandro loves Berenice. Berenice loves Demetrio. Demetrio loves Selene, who returns his love. Arsace also loves Selene. Trouble is, Berenice is queen of Egypt, so what she says goes, unless, arguably, she has been instructed otherwise by Fabio, the Roman envoy, who wants Alessandro to marry Berenice for political reasons. All this gets increasingly tangled in two and a half hours of vivacious music and is eventually resolved with a gracious ending in the opera seria mould.

Cummings and the orchestra knock it out of the park: this is a pared down Handelian orchestra (strings, two oboes, bassoon and continuo), but the paucity of wind instruments is more than compensated for by vivid dynamics and a rhythmic impulse that keeps you on your toes throughout the evening. Perhaps better than anyone, Cummings understands how to keep this music light and airy while maintaining the excitement level, helped in no small measure by the trio of continuo players on stage, with Jonas Nordberg’s archlute especially prominent in keeping the energy up even in the slow recitative accompaniments. James Eastaway also deserves a mention for a gorgeous oboe solo in Act 3.

The seven singers all put in their share of energy. Jacquelyn Stucker’s Alessandro took the crown for pure vocal beauty, with top notes that exuded warmth as well as clarity and balanced phrasing. In the title role, Claire Booth impressed for her all round ability, managing the rapid coloratura with aplomb with an especially strong lower register, stamping her voice with authority, injecting emotion into even the quickest lines and producing good variation between passes of the da capo arias. Patrick Terry was perhaps the strongest of the other high voices, in spite of the hapless nature of Arsace, who is very much cast as the fall guy. Alessandro Fisher impressed with a strong, flexible tenor as Fabio.

But here’s the first Achilles heel: we had a critical shortage of audible consonants. I could understand the odd line of each aria, but only by concentrating extremely hard. The recitative was scarcely better: if I hadn’t read the synopsis thoroughly in advance, I would have had no idea what was happening. This is a little known work with intricate vocal lines, being performed in English translation without surtitles: that requires the musical director to pay enormous attention to diction. This seems not to have happened here, in notable contrast to The Monstrous Child, my previous excursion to the Linbury and also an English language performance without surtitles.

Director Adele Thomas and designer Hannah Clark stage everything in Handelian powder-and-wigs around a single, curved, green sofa which spans the whole width of the stage. The costumes for Berenice and Selene are pure eye candy: stunning floral prints beautifully cut over enormous panniers. The costumes for the men can best be described as “motley”.

The second Achilles heel is the choice of production aesthetic: Thomas decides to play the whole thing as slapstick. If you’d taken the continuo players off stage, showed someone a video with the music muted and asked them what they were watching, the probable answer would have been “Gilbert and Sullivan”. It was entertaining enough for the first twenty minutes or so, but not for a full evening of opera: Handel’s music has the potential for great emotional range, and two and a half hours of it demands more than overacted caricature and pratfalls, however energetically and engagingly these are delivered.

It could have been so much better. With an entertaining story, good visuals and musical and vocal performances up to an extremely high standard, this could have been an outstanding evening: indecipherable diction and limited acting expressivity made it a near miss.