One of the most fondly remembered chapters in JRR Tolkien's The Hobbit is Riddles in the Dark when Bilbo becomes lost in a tunnel and meets Gollum for the first time.
Gollum plays a game of riddles with Bilbo to reveal a way out of the tunnel, while worried that he can't find his ''precious'' - the One Ring.
In 2012 in Wellington there are no riddles from Andy Serkis to explain why he's reprising the role of Gollum.
''Gollum's never really left me, and he's always been lurking under my skin and there's always been the possibility of returning to him,'' he says.
''But to actually finally get back to do it - a very strange thing, kind of, happened, really. Over the years, Gollum's become so, sort of 'owned' by the public, and in the public domain he has become such a well known character, that to re-possess him, I suppose, was to grab him back and say, 'Right, I've got to get back inside the mindset and really play this character rather than doing a pale imitation of a hundred other persons' imitations of what I did originally.''
One of the first scenes Sir Peter Jackson shot was Gollum the riddle game with Bilbo, played by fellow British actor Martin Freeman. ''I think I can safely say I was the first person in the makeup chair on The Hobbit. [Riddles in the Dark] was a great way in to the story, because it's such a chamber piece, that chapter from the book, where Gollum's a very concise entity.
''Also it was a great way for Martin, who is about to embark on playing Bilbo, to have to play opposite one other character rather than have to jump into lots of scenes with 13 dwarfs and a goblin king and hundreds of people.''
Serkis remains keenly aware that in playing Gollum, he was involved in the pioneering development of motion capture technology.
He's since developed further with King Kong, Tintin and Rise of the Planet of the Apes.
''The whole process of performance capture is [still] so in its infancy... The technology which went along with the acting performance opened up the whole world of visual effects to me, and that side of film-making.''
But the experiences also made him want to direct. As he explains this, he is taking a short break from filming an action scene involving orcs and elves.
He got the unexpected opportunity when Jackson asked him to be second unit director on The Hobbit - only a few weeks before filming was to begin. ''I was only supposed to come down to [New Zealand] to reprise the role of Gollum for two weeks.''
Instead he was in New Zealand for more than 18 months.
''Pete's known I've wanted to direct for some time now. I've been directing video game projects, theatre and short films and so on. I have a production company, and I'm setting up to shoot my first feature. Little did I know that my first feature film was going to be The Hobbit. So it was really an extraordinary offer.
''I jumped at the chance to work with him, and I suppose what Peter wanted was - because I've been through the whole process of working on Lord of the Rings - he knew that I understood the world of Middle-earth.
''The second unit on this job is very different to a normal film's second unit, basically. We're not just shooting action, we're not just shooting inserts. We get a lot of principal cast, we're doing a lot of drama scenes, we do big battle scenes, we do aerials. It's a very wide, varied palette of work that we have to do.
''Pete wanted me to do it to be his eyes and ears, have his sensibilities. We have had a very easy relationship with each other. I get a briefing from Pete every day, we exchange thoughts, he's constantly watching what we're doing, we can banter backwards and forwards, and he can very quickly achieve what he wants and I'm there to serve him completely.
"So it's been a huge learning curve for me, because normally for a director's first film you're shooting for maybe five or six weeks on a very low budget with a digital camera, or you're doing something contained and small, not working on the biggest film on the planet. It's literally like just passing a driving test and then being given a Ferrari. Or not even having passed a driving test and being given a Ferrari.''
And with Serkis still best known as the model for computer-generated characters, he can largely walk around anonymously compared to other stars of The Hobbit and The Lord of the Rings.
''I love it because what I have always adored about acting is the art of transformation.
''Performance capture, for an actor, is such an amazing tool to help create a performance because you can disappear into the role 100 per cent. For me, that's what I love about acting.
''There are actors who possibly couldn't contemplate the idea of not having their face on screen and that is their tool in that expression. But you communicate stories and characters in lots of different ways, through regular drama, through animation, through actors' performances driving emotionally truthful and engaging characters.
"It happens in lots of different mediums and this - I think the great thing about performance capture is now it's being regarded as an actor's tool as opposed to a visual effect. And that's been the big journey, really, over the last 12 years. Now it is considered a tool for just another way of recording an actor's performance.''
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