Terry Pratchett’s Nation is a novel for young readers, which brings the author’s characteristic wit to bear on some fundamental questions to do with faith and identity.

But while in Mark Ravenhill’s adaptation there are moments of spry comedy and gorgeous spectacle, there are also times when one feels as if one’s watching a hastily devised school play.

On the Pacific rim, in the second half of the 19th century, a young man called Mau returns to his people after a period spent in isolation. A storm disrupts his homeward journey. This storm also wrecks the boat carrying a teenage Briton to visit her father, a colonial administrator. She is washed up on Mau’s island, changes her name from Ermintrude to Daphne and, accompanied by a profanely talkative parrot, slowly goes native.

There are echoes of The Tempest, and of other classic desert island dramas — here a touch of Lord Of The Flies, there a nod to Robinson Crusoe. But the story is actually pretty slight, and its unfolding manages the unusual feat of being both glib and confusing.

The highlights of Melly Still’s production are the fabulously rich design she has created with Mark Friend, which incorporates Yvonne Stone’s sinister puppets, and dreamlike projections by Jon Driscoll and Gemma Carrington.

But other aspects are unsatisfactory. The dancing feels ungainly, and the Olivier’s revolve is overused. Adrian Sutton’s songs, instead of propelling the story or providing an interesting counterpoint, sound twee. When we’re treated to a burst of Handel, the weakness of the new tunes is uncomfortably emphasised.

The performances are wholehearted. As Mau, Gary Carr is muscular and engaging, while Emily Taaffe endows Daphne with presence, though she’s a touch strident. As the naughty parrot, Jason Thorpe is an enjoyable mosaic of mannerisms; he looks like Gary Rhodes but expresses himself more like
Bernard Manning.

This is no small point. Filtered through Ravenhill’s luridly playful consciousness, Nation is not really suitable for young children. Yet teenagers may feel patronised by it.

The play touches on big themes: imperial conceit, environmental apocalypse, the conflict between modern science and the seductions of religion and superstition. But these are handled with little sophistication and sometimes with a cloying worthiness. In the end it’s the five-star design that redeems a production rather short of moral and emotional heft.
Until 28 March. Information: 020 7452 3000.