The Chronicles of Narnia: Prince Caspian (PG)

Prince Caspian begins with a long, piercing scream, which seemed to continue in my head for the rest of its exorbitant two-and-a-half-hour running time.

Disney, the studio behind the franchise, evidently mean to step into the vacancy left by Peter Jackson's Lord of the Rings trilogy, but this film looks limp and weedy in comparison. For all its sword and sorcery and flights of fancy, the film remains stubbornly earthbound.

A prologue reacquaints us with the quartet of siblings, the Pevensie children, whose adventures occupied the first film, The Lion, the Witch and the Wardrobe. The place is wartime London, and our far-from-fab four are waiting to board a tube at The Strand; the train roars past the platform and transports them to the "magical" kingdom of Narnia, where dwell centaurs, dwarfs, talking badgers, swashbuckling mice and river gods. Some trip. No wonder Boris Johnson has banned alcohol on the Underground. Time doesn't mean very much in this world – the children haven't been to Narnia in 1,300 years – though one feels pretty certain that no English schoolboy of the 1940s ever said: "Had it sorted."

The Pevensies first save a dwarf (Peter Dinklage) from drowning, then come to the aid of Prince Caspian (Ben Barnes), fleeing for his life after his wicked uncle (Sergio Castellitto) has usurped the throne and ordered the murder of his nephew. There follows some unbelievably tedious to-ing and fro-ing as the good guys prepare to take on the bad.

The wicked White Witch (Tilda Swinton) appears briefly, seemingly encased within an ice-floe, and almost manages to seduce the eldest Pevensie, Peter (William Moseley). The virtuous are represented by an outsize lion, Aslan, dispensing comic-book paternalism and annoyingly voiced in sonorous, avuncular tones by Liam Neeson. Narnia itself is supplied by the majestic rolling scenery of New Zealand, where the big set-piece battles aim for the sweep of Lord of the Rings but constantly fall short in terms of excitement. It could hardly be otherwise: whenever Caspian and friends look to be outnumbered, the story simply makes a knight's move into fantasy and enlists the trees and the rivers to help defeat the forces of darkness.

The Lion and the Witch are on hand, but I saw no sign of the Wardrobe. There is something stiff and wooden here, however; just check the acting standard of the Pevensies, all hollow voices and awkward eye movement. And as for Barnes as the Prince, could they have picked a more blandly handsome actor? He actually looks less real than Rupert Everett's Prince Charming in Shrek 2 – talking of which, Shrek was the directorial debut of Andrew Adamson, who seems to have undergone a kind of creative lobotomy in the meantime. Instead of Shrek's jaunty irreverence and slick comedy he gives us messianic piety and a sliver ofboy-girl romance that feels even less sexy than Harry Potter. Kids under 12 may just buy into its soppy rites-of-passage homily; everyone else will be checking their watches and wishing themselves out of this turgid make-believe.