Most of the creature design was by Weta Workshop’s team of six designers, closely supervised by Richard Taylor and Peter Jackson. I contributed a few drawings of Treebeard and Gollum and other denizens of Middle-earth but the more crucial part of the process was the production of large numbers of Plasticine models, culminating in a highly detailed figure – for Gollum – and a full-scale puppet version of Treebeard’s head and shoulders, or the forks and branches that make up that part of his anatomy.

I have no doubt that it won’t be long before the actor behind a digital character is awarded an Oscar

These were both at Hobbit scale, or the size they would appear to us if we were hobbits, so that the actors playing Merry and Pippin – Dominic Monaghan and Billy Boyd – could be filmed sitting among the branches and conversing with the Ent who has just rescued them.

As soon as an approved design model is made, work begins on creating the digital version. The model is scanned, which gives an accurate, though not very high resolution CG model. This forms the basis for the very simplified versions used for pre-visualizing all the animated sequences, essentially animated story-boarding, and these will go through many iterations before becoming a definitive guide, both to the shooting crew and to the animators.

The animators will use either motion capture of a performer covered with tracking markers, or key-frame animation, or a combination of the two. In the case of Andy Serkis’ ground-breaking portrayal of Gollum, the whole process went through an evolution from simple rotoscoping (replacing a filmed image of the performer with a matching animated one) to trying to capture every detail of the actor's performance and facial expressions.

There has been some controversy over how much of the finished scenes is the work of the animators and how much the work of the performer, but having witnessed the incredible work of both I have no doubt that it won’t be long before the actor behind a digital character is awarded an Oscar.

The Creatures department at Weta Digital was responsible for turning the design of the characters into something that could move convincingly, with digital bones, fat and muscles.

Treebeard had to be able to move without breaking into pieces, which raises the question of how flexible his bark should be. To avoid him looking too rubbery, the bark was separated into plates secured onto a more flexible subcutaneous layer, and moss, ivy and ferns added for cosmetic effect.

Thousands of hours are spent creating and nuancing all the elements in one figure and much of this process was far too technical for me to even begin to understand. At various points along the way, all the code is sent to 'The Render Wall' to be processed into something that can be viewed as a work in progress. It isn’t unusual for this to happen well over a hundred times before the shot is finalized. The whole process was overseen by Jim Rygiel and Joe Letteri.

My role during this part of the production was to produce artwork, mainly in Photoshop, as a guide for the compositors who are creating the finished shots. It is a quick way for Peter to be able to communicate what he would like to see. He will hand over the shots as he edits the film, and give a brief description of what he is looking for – many of the shots are of actors against a green screen – and artwork will be sent for his approval a couple a days later.

The fact that I had played a part in conceiving and designing the sets and miniatures enabled a degree of continuity and realism which helped to ground the film in a believable world. On a film set in a historical period, the design process would start with the accumulation of large amounts of reference material, but when the film is set in an imaginary world that material needs to be generated by conceptual designers.