A prestige production that took over five years to reach the screen, "Otherworld" is an animated adventure based on the medieval Welsh legends known as The Mabinogi.

Opening with a live-action sequence in which three teenagers Lleu (Matthew Rhys), Dan (Daniel Evans), and Rhiannon (Jenny Livsey) discover a portal to the Otherworld in the middle of the ocean, Derek Hayes' film morphs into traditional line-drawn animation sequences in which our heroes are transformed into fantasy characters based on the Mabinogi stories.

In an age when animated is synonymous with 'digital', the film's traditional visual effects hold their own, with an innovative flair that captures the magical elements of these tales.

Offering some quite unexpected flashes of bloodthirstiness and a weighty seriousness that's in keeping with the film's medieval origins, the film's animators manage to distinguish this fantastic tale from bigger budgeted, but far mushier, cartoon fare.

What lets the production down, though, is the script's tendency to tie itself in knots. The central idea of the story is that each of our flesh-and-blood heroes finds that their real-world problems are paralleled in the animated Otherworld.

Yet by failing to give us enough background to these characters before they enter the magical realm, the dynamics of the script fall resoundingly flat - something that's only exacerbated by the fact that none of these characters look enough like their animated counterparts to encourage any kind of identification.

As the brouhaha surrounding "The Lord of the Rings" generates a huge revival of interest in fantasy, the timing for this animated adventure was nigh on perfect. If "Otherworld" had prized character and plot over animation, this painstaking attempt to bring the stories of the Mabinogi to a wider audience might have struck box office gold.

As it stands, it's simply a missed opportunity.