LONDON.- For those who find regular love triangles too pedestrian, quadrangles and pentagons are also available. Unconventional arrangements are the order of the day in a dynamic revival of Andrew Lloyd Webber’s “Aspects of Love,” which opened Thursday at the Lyric Theater in London. This two-act musical, inspired by a 1955 novel by David Garnett, pits a young man against his uncle in a tussle for the affections of a mercurial actress; it is a camp, unapologetically amoral romp featuring blithe betrayals, intrafamilial partner-swapping and questionable intergenerational flirtations. (It is a lot raunchier than Lloyd Webber’s most recent work, which invited the audience to “sing unto the Lord with the harp” during the coronation of King Charles III.)

This “Aspects of Love” is exquisitely produced and superbly performed, but — like many a real-life libertine — it eventually buckles under the weight of its excesses.

We begin in 1947, in rural southwestern France, where Rose (Laura Pitt-Pulford), a struggling actress, meets Alex (Jamie Bogyo), an adoring fan. Alex, 18, invites Rose to stay with him at a villa owned by George (Michael Ball), his rich uncle, and the two fall in love. But Rose then unceremoniously ditches Alex for his uncle, to the dismay of George’s partner, Giulietta (Danielle de Niese), an Italian sculptor.

We check in with the four at intervals over the next 20 years, as the action moves to Paris, then to Venice, then back to the French countryside. Alex and Rose are never quite able to leave each other alone. To further complicate matters, both of them also get intimate with Giulietta. Cue jealousies, recriminations — and plenty of drama.

Pitt-Pulford is charismatic and engaging as Rose. A vibrant stage presence, she is by turns imperious, flighty and needy — the quintessential histrionic thespian. Bogyo’s portrayal of a callow, love-struck young person is convincing; he is frequently exasperated, and we sympathize with his predicament because he is too inexperienced to know any better. Ball — who played Alex in the musical’s original production, in 1989 — is outstanding as George, a genial, urbane bon viveur who assures the teenage Alex that there are plenty more fish in the sea (“Life goes on. Love goes free.”) His serene sanguineness is the show’s beating heart.

The production is immaculately put together, and John McFarlane’s luscious set design incorporates beautiful painted backdrops depicting Parisian street scenes and rural landscapes. A rotating stage is deployed to good effect during romantic scenes to evoke the head-spinning euphoria of early love.

Although the show is practically flawless as an audiovisual spectacle, the story gradually wanes. Things take an unwholesome turn in the second act with the introduction of Jenny, George and Rose’s young daughter (played first, as a young child, by Indiana Ashworth and later, as a teenager, by Anna Unwin). Jenny develops an intense crush on Alex, and the ensuing will-they-won’t-they is skin crawling. The bawdy, pantomimic esprit of the first act gives way to awkwardness; an audience that had been positively purring at the intermission was palpably uneasy with this storyline.

To account for this somewhat jarring transition, we must turn to the novel on which the musical is based. Its author, Garnett — known as “Bunny” to his friends — was a member of the Bloomsbury literary set notorious for their cavalier attitude in matters of romance. His parents had lived in a menage a trois with a young actress, and eccentric sexual behavior was a recurring theme in his life. In 1942, he married Angelica Bell, his former lover’s daughter, whom, in a letter 24 years earlier, he identified as a potential spouse when she was just a baby.

Garnett’s novel may have had a certain transgressive purchase in the mid-1950s, at the dawn of a revolution in sexual mores. But from a 21st-century perspective, the story feels, at best, a kitsch curio. There is something quaintly naive about dignifying such flawed romantic entanglements — puppy love, infatuation, grooming — with the sentimental earnestness of the show’s soppy signature tune, “Love Changes Everything.” In truth, the ditty that best captures Garnett’s ethos is the “Hand Me the Wine and the Dice” from Act 2, an upbeat anthem to living in the moment.

In both the novel and onstage, the characters are so thinly sketched that it is hard to take their emotions seriously, especially given the conspicuous discrepancy between their professed intensity of feeling and the fickleness of their affections. Maybe the real subject of this musical is not romance per se, but overweening egotism — what we would nowadays call narcissism. It is an enjoyable ride, and there is just about enough comeuppance to satisfy the moralists, but one is left wondering, to paraphrase Tina Turner, what love has to do with it.

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‘Aspects of Love’

Through Nov. 11 at the Lyric Theater in London; aspectsoflove.com.

This article originally appeared in The New York Times.