The Poisoned Kiss is Vaughan Williams’s forgotten opera: this is the first complete recording. It was written in the late 1920s when he was at the height of his powers and about to launch into the great stylistic development that gave us a new perspective on his music. When, in 1927, he began writing The Poisoned Kiss, he was already at work on his Falstaff opera, Sir John in Love, and was beginning to make sketches for Job. This inventive opera reflects the exuberance of his inspiration even in a project that he admitted was the only work he did not show to Gustav Holst, on the grounds that his friend would not understand why he had chosen such a far-fetched subject.

The composer chose his friend Evelyn Sharp, sister of Cecil Sharp, leader of the folk-song movement, to write a libretto based on a short story by Richard Garnett (developed from one by Nathanial Hawthorne), about a beautiful princess who lives on poison. But the treatment – in deplorable verse – undermines the lightness intended. The pair had in mind the operettas of Gilbert and Sullivan, yet in the choice of anachronisms – references to ‘going to the pictures’ and the like – the result is coy and self-conscious, never witty or pointed in a Gilbertian way. In two bouts of revision in 1936 and 1955, Vaughan Williams eliminated the feeblest of the anachronistic references, but there are still too many embarrassingly unfunny lines.

This recording helps to rehabilitate the opera by eliminating virtually all the spoken dialogue, (it’s printed in the libretto, in shaded sections, so you can choose to read it or not). A detailed synopsis might be even more helpful: Stephen Connock describes each of the 39 numbers and the story around it.

Neither Vaughan Williams nor Sharp could work out the right balance between comedy and the central romance – the love between Tormentilla, brought up on poison by her magician father, Dipsacus, and Prince Amaryllus, son of the Empress Persicaria. In Tormentilla there is a similarity not only to Gilbert’s comically self-regarding heroines but also Cunegonde in Candide, yet the treatment of her is heavy-handed.

Though Vaughan Williams planned this as a light opera, the music belies that. On first listening I found the libretto tiresome, but later hearings have revealed how mere doggerel leads to a score rich in one delectable musical idea after another; each number is beautifully tailored, never outstaying its welcome. At almost two hours of music, the opera is too long (and would be even longer with dialogue), but the inspiration never flags.

Charm predominates, with tender melodies like that in the Act 1 duet of Amaryllus and Tormentilla, ‘Blue larkspur in a garden’, and a surging emotional climax in the ensemble which crowns Act 2, when their love leads to the passionate poisoned kiss and the threat of death to Amaryllus. Was Vaughan Williams taking the story of forbidden love more seriously than intended? I must also mention the direct echoes of Sullivan in the multi-layered ensembles and patter numbers, which come nearer than anything to achieving the lightness aimed at.

In the end, in true Gilbertian fashion, everyone is paired off, even the three Hobgoblins and the three Mediums. Amaryllus defies death, thanks the antidote provided by the foresight of the Empress, his mother, and marries Tormentilla; the Empress is paired off with her first love, the magician – and Tormentilla’s father – Dipsacus; and the servants, Angelica and Gallanthus, fall madly in love.

Whatever the shortcomings of the piece, no lover of Vaughan Williams’s music should miss hearing this wonderful set, with a strong and characterful cast superbly led by Richard Hickox, and with atmospheric sound enhancing the musical delights. Janice Watson as Tormentilla sings with sweetness and warmth, while giving point to the poisonous side of the character, and James Gilchrist makes an ardent Amaryllus. Pamela Helen Stephen and Roderick Williams are totally affecting in their love music, and Neal Davies is firm and strong as the magician, Dipsacus.

Though the Empress does not arrive until Act 3, she dominates proceedings, following the G & S tradition for formidable contraltos: here the veteran Anne Collins is larger than life. The hobgoblins and mediums are cast from strength, the chorus is fresh and bright, and the BBC National Orchestra of Wales plays with winning warmth. The success of this set makes me wonder whether The Poisoned Kiss might find its place as a concert piece with narration between numbers, in the way that Bernstein finally presented Candide.