Stephen Sondheim’s final musical is a passion project in more ways than one. An adaptation of two films by Luis Buñuel, it reflects his lifelong love of cinema. Sondheim began mulling over the idea more than four decades ago (with playwright-director James Lapine) and started working on it almost a decade before he died in 2021.

This production’s programme notes speak of its development as a slow process with email exchanges between Sondheim, director Joe Mantello and book writer David Ives. A parting gift from Sondheim, left in draft form, it makes its European premiere after a run in New York in 2023 – two actors from that production are joined by an otherwise new cast. It is full of adventurous imagination, with some signature Sondheim sparks, but the trouble spots are still clear to see.

Its plot is a blended rearrangement of the 1972 social satire The Discreet Charm of the Bourgeoisie, in which a group of idle rich types make plans for dinner which are repeatedly foiled, and The Exterminating Angel (1962), about the aftermath of a party in a house where the servants have fled and the diners are mysteriously trapped. The first act is based on the former film, the second largely on the latter.

Mantello’s production begins energetically with wryly satirical humour about the charmed lives of the 1%. There are funny exchanges in the first restaurant they visit, Cafe Everything, which falls woefully short of its name. Subsequent restaurant scenes are a pale reflection, bordering on farce, and where The Discreet Charm is filled with surreal hauntings and dreams within dreams, this does not translate with the same air of intrigue on stage.

The actors are vibrant nonetheless, though some are wobbly singers. Paulo Szot, as ambassador of the imaginary South American nation Miranda, has an impressive operatic depth to his voice and Chumisa Dornford-May, who plays the revolutionary Fritz ­– a trustafarian who is given an unconvincing romance with a soldier – is a strong singer, too, while Rory Kinnear is fun as the arrogant Leo Brink.

But as the show travels from movement to stasis, with emphatic repetition that is as existential as it is literal, it falters in momentum and brings longueurs, despite urgent warnings about the end of the world. Musically, the sound is unmistakably Sondheim’s but there is no one great song, not even one memorable song. There is heartiness and humour but little of Sondheim’s usually intimate or penetrating psychology. Lyrics contain some good satire but also banal rhymes such as “Ladies and gents before we dine / Let us thank the lord for cheese and wine”. Recitative with deliberate dissonance seems strained at times.

The unravelling after the dinner of the second act gains significance in its metaphor and becomes a dystopia in a drawing room: these spoiled rich people’s inertia leads to their own imprisonment once the servants have left. But the class satire is not potent enough. The couples speak in disparaging ways about the servants who, in the film, seem quietly fulminating (one even speaks of her hate of Jesus) but who do not have the same alienation and contained rage here. They are comical stock figures without sharp edges until we get to the ambassador’s home when his butler bluntly spells out his frustrations.

If the script and music lack fizz, there are at least the visual thrills and spills of David Zinn’s set, with a blinding luminosity giving the effect of a hallucination, and the realist setting of the last act in the ambassador’s opulent home abounding with surreal edges.

Is this whole scenario a dream in the vein of Jean-Paul Sartre’s Huis Clos, a play in which hell really is other people when they become stuck in the same room for eternity? Here We Are should leave you scratching your head but for all its interesting ideas on life and death, rich and poor, it melts away rather too quickly afterwards.