A lot of time to Phil

There's no question this six-hour dramatisation of Philip Pullman's fantastical and provocative epic is the National's most ambitious ever production. Whether the results merit it is more doubtful, since the trilogy's multi-layered narratives and thematic complexities are undeniably happier on the page than on stage.

Much of the ambition in Nick Hytner's robust production is channelled into visual effect rather than narrative subtlety, with an awesome, hi-tech revolving stage and seemingly infinite number of sets. Yet these solid, ever-changing backdrops also sometimes detract from the otherworldly quality of Pullman's ungodly universe and occasionally overwhelm the actors.

Perversely, the smaller details and more simple stagings enchant the most: the ethereal, animated puppet daemons; the imperial, white masked bears; the fabulous descent of the boatman onto a dark stage.

Nicholas Wright's adaptation doesn't flinch from Pullman's humanist attack on religious orthodoxy, but struggles to establish its intricate subtexts. Yet one can't ignore that this is a production also aimed at teenagers, and happily Anna Maxwell Martin is a perfect Lyra: stroppy, sensitive and utterly compelling, with her growing intimacy with Dominic Cooper's Will thick with adolescent wonder.

The final 'half' meanwhile, in which Lyra and Will visit the underworld (powerfully denoted with just dry ice, a huge mirror and a dozen grey children), is unforgettable; rich with theatrical magic and almost unbearably moving. Remember His Dark Materials for this, and applaud what the National has set out to achieve.