You're a tall man but you play a dwarf - is it strange seeing yourself looking so short on-screen?
We were actually bigger versions of ourselves than when we were actually shooting it so I never felt small but when you watch it back and you see the reduction in size, you think, "surely I’m not that small?" It does slightly kick you in the guts a little bit because I see the character as having high status. He thinks a lot of himself and dwarves have big egos so when you see yourself a little bit diminished around other characters... He’s got a bit of a chip on his shoulder.
Does the hair help you summon up Thorin's kingly presence?
The hair helps, yes. It was interesting because when we were putting him together and giving him a look, there was a temptation to over-decorate him with jewellery and finery to give him that kingly quality but actually by taking it away and making him look like a warrior, it seemed to give him more status which makes him interesting.
Would you make a good warrior?
I‘d probably need feeding a bit better than I am now but yes, maybe. I think my fighting skills have certainly been improved by working with Peter Jackson. I started out with a really great stunt double but by the end of the third film Peter was not really putting [him] in – he was letting me do all the fight sequences and I took it as a compliment but there’s a part of me that hopes it’s good enough. It certainly pushed me - I cried and I bled and I sweated so hopefully it’ll all be there in the third film.
Have you done your own stunts before?
When I worked on Robin Hood I used to do as much as I could and then when I went into [Sky1 series] Strike Back I was able to say to them I’d really like to do everything myself and they did let me so you could really experience what the character’s gone through - right up to the waterboarding sequences which became a little bit controversial - but I just wanted to know what it felt like.
Have you ever been really scared?
The scariest stunt I’ve ever done was on Captain America. We were doing some underwater sequence. I was in a submarine and Chris Evans had to break the glass and the water had to fill up quickly in the submarine. That was really scary because I was supposed to take a breath of air before the water came in but when you’re acting like that you speed up your breathing so I was taking in water and it was really terrifying. I think they got three takes out of me before I said "I’m sorry, I can’t do another one."
How do you rate Martin Freeman as a leading man?
He’s just brilliant. He’s so inventive and he keeps the atmosphere on set really buoyant because he’s got a natural sense of comedy, as Martin but also as Bilbo Baggins. He really experiments with the role and he makes me work in a different way. He’s always having a bit of a laugh but when it comes to doing the serious stuff he can always pull it out the bag. He’s incredibly moving in the third film and that’s always surprising because you think you know Martin to be a great comedian but he’s also a great dramatic actor as well. I really enjoyed working with him and I think a lot of the evolution of Thorin is down to the way that he portrayed Bilbo. There wouldn’t be a Thorin without a Bilbo.
Any stand out moments of hilarity...?
He was just very good at being a little ninja Bilbo. Behind the scenes he’d have a little crack at everybody who was a bit bigger than him but he’d try his kung fu ninja moves on everybody which always made me laugh.
His Sherlock co-star Benedict Cumberbatch is also in the film...
I actually got to work with him face-to-face which I didn’t think I would because he was doing a voice in a room and he said it himself that he was a little bit disconnected from the shoot. But I went in one day to do some of the dialogue Thorin has with Smaug at the end so I saw him working and we delivered lines to each other which was a real treat. He’s an extraordinary actor and has a great following and thank goodness because it all adds to the popularity of the film.
Will it be hard to let go of Thorin when the trilogy ends later this year?
I think he’s one of those characters I’ll probably never stop thinking and talking about. He’s infinitely fascinating. There is an end to his character - if you’ve read the book you know how it ends - but I think he’s been a character I’ve been quite close to over the past couple of years.
What can you tell us about the third (and final) Hobbit film?
I think it’s going to be a slightly shorter film than the other two. It’s the final instalment – the wrapping up of all the loose ends. There’s a lot of madness in there, certainly for Thorin. He goes into a little downward spiral and it’s called There and Back Again so you see Bilbo go home. Lots of fun things to happen and it's also probably the final time that Middle Earth will ever be seen on the big screen so a bit of a nostalgia trip.
The Hobbit: The Desolation of Smaug is out on DVD on April 7. Read the Radio Times review here