While a major mounting of Oliver! takes over the main house, Curve Artistic Director Nikolai Foster has made a small show on a big scale for the studio space. David Wood’s adaptation of The Witches preserves the British seaside whimsy and Norwegian melancholy of Roald Dahl’s novel and in Foster’s hands it’s an energetic, wonderfully funny and often unsettling ensemble piece.

Beginning with the promise that not all stories end happily, the company sing and tumble their way through the induction of Boy (Fox Jackson-Keen) into the hidden world of child murder. The subject matter is sensitively handled for a children’s show; an early tense sequence as Boy comes down from a treehouse, mesmerised by the enormous snake curling its way around the neck of an immaculately dressed – and gloved – lady, is genuinely scary, letting the scene linger until the snake lashes out. The scares are strengthened by the tenderness allowed to develop between the forthright and eminently sensible Grandma (Karen Mann) and her wide-eyed grandson, she shielding her traumatised ward from a growing number of threats.

But while there is a suitably Dahlian undercurrent of darkness, the predominant tone is festive. A set consisting of a grand piano underneath a spiral staircase leading up to a platform level is littered with instruments and framed by brightly lit pillars and fairy lights. The whole ensemble contributes to the constant score (including, in one brilliantly choreographed sequence, tagging each other in succession off the piano and onto the stage). The richly drawn caricatures – the cartoonish witches with fright wigs in place of bald heads, the affected Liverpudlian Mrs Jenkins, a suitably pompous concierge – are full of the life of Quentin Blake illustrations and their silent slapstick and shrieking histrionics propel this energetic show.

Given the size of the ensemble and of the set, the spectacle is impressive. Neil Henry’s magic design features plenty of pyrotechnics and a wonderful closing illusion with Sarah Ingram’s Grand High Witch disappearing into a shallow cooking pot, earning a spontaneous round of applause for the ‘how did they do that?’ factor. Other stunts, including Boy firing his pet mouse from a cannon through a prop book or a witch being frazzled, are no less effective in their speed and quick changes. But the real magic comes during the second act, once Bruno and Boy have been turned into mice (ears, whiskers and tails). Rather than attempt to literalise the size difference, Foster makes clever use of the upper level to have Grandma talking down her to her grandson; of a number of oversize props; and of Jackson-Keen’s extraordinary physical versatility. This mouse hangs upside down from bars, somersaults from a standing start and vaults from the top of the spiral staircase. When on the run from the witches (and later from a huge projected cat) Boy helps Bruno navigate the set in entirely unexpected ways, creating new kinds of space accessible to the transformed figures.

The production works best when the ensemble operates together. The meeting of the witches is driven by Ingram’s exuberant, German-accented and surprisingly operatic performance, but made hilarious by the improvised bickering, cackling and muttering of the witches. The restaurant scene, as two disgusting chefs slop food onto plates and spit on them for gravy, is a slick musical sequence, with the Witch’s impatient tapping of her cutlery providing percussion and a waitress manoeuvring the different components of the scene. A final, rather saccharine Disney-like song is less musically interesting, but gives the excited children in the audience a chance to high-five the cast and go out on a bang after a quieter, final moment between the mouse and his grandma as they realise they both only have a few years left to live. The communality of the ensemble translates into an affecting and warm finale.

Foster’s production is very much in the spirit of Dahl, and a continually inventive, amusing evening. While the graphic evocations of the car crash that kills Boy’s parents and the more sinister witches may be too much for younger children, for older children (‘and their brave grown-ups’) this is a funny and surprisingly sophisticated rendition of Dahl’s dark fairy tale.