UK fans and critics have had their first taster of James Cameron’s epic sci-fi actioner Avatar, with 15 minutes worth of preview footage shown at four special screenings at London’s IMAX cinema.

We were among the audience of big glasses-wearing geeks at one of the screenings, and can confirm that the footage looked awesome. Of course, these sort of sneak previews are a useful publicity device because they prompt you into saying things like “It looked awesome!”, though few filmmakers are confident enough to screen so much footage so far in advance (the movie opens on 18 December).

James Cameron (who gave a short video intro assuring us that there were no major spoilers in the scenes we were to witness) has every right to be confident though – this really looks like it could actually live up to the hype and take 3-D moviemaking to the next level.

The movie is set on the rainforest planet Pandora in the 22nd Century which contains both friendly natives and furious beasts. Sam Worthington’s crippled marine Jake Sully is a human visitor to the planet, hoping to find a cure for his condition. But in order to survive on Pandora, humans must take on the form of blue-skinned ‘avatars’….

The footage we saw included a live-action sequence in which Jake is reassured by Sigourney Weaver’s doctor as he undergoes the transformation to the avatar state, and a subsequent tense scene in which Jake wakes up as the towering blue-skinned creature – and promptly becomes out of control.

Other scenes contained action-packed fantasy footage as Worthington's avatar comes up close and personal with various beasts on Pandora – including, in the most thrilling scene, a wrestle with a pterodactyl-style winged creature.

The 3-D – even just in the live action scenes – is staggering, but crucially it does seem as if there are actually intriguing characters to go with the special effects. Anyhow, the preview certainly did the trick: it’s safe to say that, as everyone returned their 3-D glasses, there were few who weren’t aching to see the complete movie...

Avatar is released in cinemas worldwide on 18 December 2009.

You can view the trailer here: http://www.apple.com/trailers/fox/avatar/hd