With music by Johann Strauss the younger, the presence in the cast of Mandy Patinkin, and the co-direction of Broadway royalty Harold Prince and Susan Stroman, Paradise Found looks on paper like another smash hit for the Menier Chocolate Factory, the Southwark venue that has, over the last six years, established itself as London’s most successful incubator of musical theatre.

The Menier’s stock is at a high. Among its recent offerings, Sweet Charity is delighting West End crowds, while the Broadway transfers of La Cage Aux Folles and A Little Night Music have garnered 15 Tony Award nominations. Unsubsidised, and run with passion and energy by artistic director David Babani, the Menier is a model of commercial savvy, which prospers through careful nurturing of talent.

But with Paradise Found, its handsome run of form comes to an end. This is a dizzyingly unfashionable operetta, set in Vienna in the heyday of the Austro-Hungarian Empire. Wags might dub it a Viennetta. It’s certainly a sickly confection.

The Shah of Persia, tortured by sexual frustration, descends on the Austrian capital in the hope of adventure. He has in tow his trusty eunuch and Grand Vizier, and is received warmly by the Viennese gentry. Soon enough the Shah is infatuated with the Austrian empress, and complex manoeuvrings ensue.

The chief problem, apparent early on, is Richard Nelson’s book, which refashions a story by Joseph Roth into a lubricious farce. The opening scenes drag, unleavened by humour. Nods to The King And I, as well as a more-than-passing resemblance to Measure For Measure, only emphasise the poverty of the material and its structural mess. When the mood darkens, it’s thoroughly incongruous, a bit like splicing The White Ribbon into an episode of Glee.

The performances are wholehearted, yet wafer-thin characterisation makes it difficult to engage with them. There’s a lot of expensive, imported talent squeezed on to the small stage, and it is largely wasted.

Kate Baldwin and Shuler Hensley each make a strong impression, but they’re constrained by Ellen Fitzhugh’s lyrics, which are a mixture of saccharine banality and tacky surrealism.

Patinkin, working hard to embody the eunuch, is obliged to sing at the top of his range far too much, and seems to be channelling Mike Myers’s Dr Evil or possibly Yoda.

“Theatre is never as interesting as real life,” remarks the Grand Vizier near the end. Unfortunately, it’s an apt judgment on a musical that suffers from a nonsensical plot, a rather tired bawdiness, a lack of imaginative zest and the absence of a single really sparkling number.

 Until June 26. Menier Chocolate
Factory box office: 020 7907 7060.