Many years ago, the dwarves of Erebor, the Lonely Mountain, were driven from their home by Smaug, last of the great dragons. Thorin Oakenshield, the grandson of the last King of Erebor, has vowed to reclaim his home and called upon the dwarven clans of Middle-earth to aid him. Rebuffed, he instead plans a daring raid of a few chosen dwarves to slay Smaug whilst he sleeps. To aid them, Gandalf the Grey has promised to recruit a skilled burglar: Bilbo Baggins, a hobbit of the Shire. Their journey will take them through forests and caverns, all the while being tracked by an old enemy of Thorin's...

An Unexpected Journey is the first movie in a trilogy based on J.R.R. Tolkien's 1937 novel, The Hobbit. That's Tolkien's short novel which, by word-count, is just under a fifth of the length of The Lord of the Rings. There's been enormous controversy about director Peter Jackson's decision to split The Hobbit into three three-hour films, with a fear that there simply isn't enough story to warrant it and this will result in padding. That is the threat that constantly hangs over the film and to be fair, it mostly avoids it by making a major change: Jackson has decided to show in full Gandalf and the White Council's side-story to confront and destroy the 'Necromancer' of Dol Guldur (a storyline that takes place off-page in the novel). Whilst also controversial amongst fans, it does give Jackson a rich vein of story to mine to add to proceedings, but how successful this will be remains to be seen (this subplot is only really started in the film).

The movie opens with the older Bilbo (still played by Ian Holm) writing an account of his adventure for Frodo and narrating the destruction of the human town of Dale and the neighbouring dwarven mountain-city of Erebor by Smaug. We then have the traditional opening from the novel, with thirteen dwarves and the wizard Gandalf turning up on Bilbo Baggins's doorstep to recruit him for an adventure. By the time the young Bilbo (Martin Freeman) agrees to join the quest, a rather surprising forty minutes has passed. This sequence risks interminability, but Jackson takes advantage of the time to introduce the thirteen dwarves and give them some character traits missing from the source material. James Nesbitt's Bifur in the somewhat cynical joker of the pack, whilst Fili and Kili are the over-eager young guns out to impress their older peers. Dwalin is the bruiser and Balin the wise old - and somewhat pedantic - sage of the group (Ken Stott is excellent in the role). Bombur is fat and little more than that. The real impact is made at this stage by Richard Armitage as Thorin Oakenshield. Armitage is charismatic and has steely resolve and presence in his role, and is the standout performance of the movie (and, dare I say it, impresses more than even Viggo Mortensen as Aragorn in the original trilogy ) .

As well as showing the Necromancer stuff on-screen, Jackson has made some other changes to the story to increase the dramatic weight of events. Thorin now has his own nemesis, a mighty orcish warrior whose arm he cut off in battle. This warrior, long-thought dead, has returned and is now chasing down Thorin and his band (a bit like Lurtz in the movie version of Fellowship of the Ring, but a lot smarter and more continuously present). It's another change that I think some won't like, but as a dramatic device it worked fairly well at introducing some tension to the film. However, what was really distracting is that this orc has the exact same skin tone and texture as the Engineers in Prometheus and is likewise gigantic. His story arc is left unfinished at the end of the film, so we can assume he will return in the sequel (rather cleverly, as it provides a potentially better way of explaining a subplot in that film than Tolkien was able to do in the book).

Elsewhere the film feels a lack of cohesion: the Necromancer plot has little to do immediately with Thorin's quest, so every time we cut away to Radagast the Brown (a great performance by the ex-Doctor Who Sylvester McCoy) trying to resuscitate hedgehogs (!) or Gandalf discussing backplot with Saruman and Galadriel for what feel like nineteen hours, the movie flags. In fact, the dwarves get so bored of Rivendell (missed opportunity: someone saying, "On second thoughts, let's not go to Rivendell. 'Tis a silly place," they just up and randomly leave. Once the dwarves are back on the road together and causing mayhem, the film perks up and more fun is had, even if sometimes accompanied by some unconvincing CGI.

The scenes in the goblin caves in the Misty Mountains are entertaining, but also daft. Barrie Humphries as the Goblin King works rather better than most were likely expecting (and there's a humourous nod to Gandalf's "You shall not pass!" moment from the original trilogy), but the extended battle-and-escape sequence is too slapstick to really present much tension. This contrasts to the successful scene where Bilbo meets Gollum (Andy Serkis, on fire as always) and acquires the Ring, which is brilliantly acted by both parties and features some nice tonal variations from comedy to menace and back again.

Overall, The Hobbit: An Unexpected Journey ( ***-and-a-half ) can be called a qualified success. It has some big problems that Jackson has not been able to overcome: the storyline is too slight to sustain three hours and even with the addition of extra storylines and characters, there are some scenes which feel like wheel-spinning for the sake of it (most notably at Rivendell). There is also a near-omnipresent use of CGI in almost every scene of the movie. The original trilogy worked best when the camera was allowed to film natural landscapes or when miniatures were used to depict locations and give them a sense of reality and weight. Here, CGI is much more freely employed, often with less regard for hiding the fact it is CGI. In particular, there is a dearth of truly awesome shots of the countryside of New Zealand in all its glory compared to the original trilogy: here, even many of the landscape shots have been bathed in CGI until they glow with lens-flare. Even in 2D and at 24fps, the film has a 'faker' sheen across it than the original films, which sometimes distracts.

Fortunately, Peter Jackson has learned from the mistakes of George Lucas and has remembered to include plenty of character moments to keep things more real. Armitage is awesome, as previously mentioned, but it's Martin Freeman's performance as Bilbo which anchors the movie. His character arc (and Thorin's, which develops in tandem) is well-handled and Freeman nails this icon in a way he didn't manage with Arthur Dent (in the disappointing Hitch-Hiker's Guide to the Galaxy movie). These character and thematic moments are less-successfully handled than in the original trilogy, but still give the film some dramatic weight and tension that keeps things interesting.