An audience with Stephen Lang is like an acting master class – or perhaps a game of chess with an esteemed adversary. Not that he takes himself seriously, but the work – yes. Brando-like self-deprecation is not for him. He considers his craft a noble art. "Aside from politics, what else is there?" he says.

No sooner have we sat down than we are discussing great Shakespearean theatrical triumphs – and the odd debacle – of such luminaries as Anthony Hopkins and Paul Scofield. Lang believes the greatest King Lear he ever saw was Scofield’s. Having never seen Scofield, I veer towards Ian Holm.

In terms of character, Lang reminds me of playwright Edward Albee. He’s concentrated, intense, passionate, erudite and analytical, a master tactician at the top of his game, a film and stage buff for whom no film or production – regardless of its age or size – is too obscure. He can talk eloquently about British movies from the 1960s: Sidney Lumet’s The Hill (1965) and thirsty thespian Oliver Reed’s performance in The Trap (1966), for example, earn his plaudits.

With thousands of stage performances behind him – and a far longer memory span than mine – he can better any recollection. When I tell him I once saw Lauren Bacall in Sweet Bird of Youth on the London stage (1985) he tells me he saw distinguished stage actress Irene Worth in the same role. When I mention my pleasure at seeing Jack Lemmon on stage in Long Day’s Journey Into Night (in 1986) he cites the greatest theatrical performance he has ever seen – George C Scott in the Broadway production of Death of a Salesman.

Not that his tastes are snobbish – some of his favourite movies are The Wild Bunch (1969) and Mel Gibson’s Apocalypto (2006). His favourite actors – aside from Scott he mentions Ben Kingsley, Sean Connery, William Holden and, perhaps surprisingly, Ray Winstone – tells us of his preference for a naturalistic style. So-called bravura performers – Richard Burton and Peter O’Toole, for example – are not so much to his taste. He prefers the unobtrusive brilliance of chameleon-like actors such as Alec Guinness (he cites Guinness’ performance in David Lean’s Bridge on the River Kwai – 1956 – as one of the all-time gems) and Jason Robards. "The actor should not become more important than the role," he says.

Lang relishes not being recognised from part to part; he submerges into the characters he plays. When I meet him in his trailer on the set of Conan – currently shooting in Sofia – he looks completely different from his previous role in Avatar – and it’s not just down to the make-up department’s assiduous job. Only the blue eyes remain the same – sharp, accusing and challenging.

Of course, one of the dangers of being unrecognisable is that audiences overlook the quality of your acting. I’m reminded of John Hurt being told after The Elephant Man (1980) that he’ll never get credit for his role because nobody could see it was him. "I thought that was the whole idea," said a deflated Hurt.

Quaritch
I don’t immediately "assail" Lang with his recent standout performance as Colonel Quaritch in Avatar. I figure that Lang, although a courteous and reassuring man, is perhaps tired of the press junket surrounding it. I also suspect that he doesn’t suffer fools gladly – or otherwise.

He’s dressed as Conan’s adversary Khalar Zym – definitely the villain of the piece, although it’s not a term he likes – fresh from a scene where he has slain Conan’s father, played by Ron Perlman – an actor whom he’s known and liked for a long time. "I haven’t approached the character as a villain. Clearly there are many bad guys in the movie," he says. He sees himself as a character actor. Seldom the romantic lead, he always seeks to raise his anti-heroes beyond the one-dimensional. Lang quotes perhaps the most enduring villain of all time, Richard III. "And therefore, since I cannot prove a lover, to entertain these fair well-spoken days, I am determined to prove a villain."

Avatar cannot be overlooked any longer. Many think its theme of greedy humans plundering a planet resonates today. I take a deep breath. Was Quaritch – a muscle-bound machine soldier with a simplified vision of the enemy – a modern morality tale against the neo-conservative, colonialist agenda? I prick my own euphemism. Was it, perhaps based ever so slightly on...George W Bush? Lang’s brow furrows. He looks mortally offended. "Oh God no! Quaritch was an INFINITELY better military strategist and commander, and FAR more dynamic than George Bush," he says. "That never crossed my mind at all – no way."

Yet, he concedes, there are lessons to be drawn from Avatar. "Historically, America has been a beacon to the world," says Lang. "Yet sometimes we delude ourselves about our real intentions. Was it all about democracy in Iraq? Not exclusively. Perhaps it was more about oil, after all. However, I support the war in Afghanistan and" – here he surprises me just as I had him pigeon-holed as a liberal – "perhaps we should have finished off Saddam the first time around".