Philip Pullman's scary story of a time-wasting clockmaker's apprentice, the devilish Dr Kalmenius who appears to come to his aid, a murderous mechanical figure and a clockwork child is a small book bursting with big ideas. It has something of both the medieval morality play and the horror flick about it, and it grapples with ideas about the nature of creativity and storytelling and the transforming nature of art and love.
It is appropriate, then, that it should undergo a transformation itself and become a modern opera by composer Stephen McNeff, whose score captures all the drama and atmosphere of this eerie story. The great thing about producing contemporary music for children is that they are very receptive to it and quite unfazed by the form. They don't go: "Oh no, contemporary music, that's really hard." They just embrace it as being perfectly natural, and as good a way to tell a story as any other.
McNeff's score ensures that it is. You couldn't imagine a better way to set off this story about stories than his percussive spookiness, which gives an urgent sense of the tale all wound up and ticking mercilessly towards its end. "He has wound up the future," it is said of Karl, the clockmaker's apprentice when he chooses evil over good, a lie over truth - and so seals his own fate.
Tony Graham's beautifully sung production is superbly designed by Russell Craig, with a leaning clock tower clearly conceived by someone from Pisa and lots of masks and puppets. As a result, the eye-catching opening sequence gives a taste of the story to come: it never cuts corners and never talks down. This is an evening in which the lower age limit should be around eight; and reading the book would be advisable. All power to Unicorn Theatre for spreading its wings, and to the Royal Opera House for giving it a stage.
· Until April 3. Box office: 020-7304 4000.
