A few years ago, Guy Pearce's thought his acting career was on the wane. He was being passed over for the roles he wanted, and being offered ones he didn't. When he did work on movies as distinctive as those that had sealed his reputation (LA Confidential, Memento), it tended to be in the capacity of professional guest star: he was the kind but mildly creepy stranger at the end of The Road, and the one you don't expect to die at the start of The Hurt Locker. When the latter film cleaned up at the Oscars, the congratulations only made him feel fraudulent. "I wanted to say, 'No, no, you've got the wrong person,'" he cringes. It was, he says, a curious time. "I started to think, 'Oh, OK. I see. I'm vanishing from view a little bit.'"

All of which is surprising, coming from someone who is currently starring in a pair of award-magnet movies (The King's Speech and Animal Kingdom), a horror film bankrolled by Disney (Don't Be Afraid Of The Dark) and a prestigious HBO mini-series opposite Kate Winslet (Mildred Pierce). Right now he's in the middle of shooting Lockout, the story of an intergalactic prison break. "I'm playing a buff action hero," he says sheepishly.

So what changed? "I've always been resistant to parties and schmoozing. I've always hated the game. And I realised it has to be part of it. Sure, I was lucky to get LA Confidential and Memento, but that was 12 years ago." He thinks the financial crisis may have been partly to blame for his dwindling employment. "Actors like me, the ones in the middle, tend to lose out. People will go, 'No, not him. We need Matt Damon.'"

As Mike Young with Annie Jones as Jane Harris in Neighbours. Photograph: Freemantle Media

Since he started making a few extra trips from his Melbourne home to meetings in Los Angeles, things are looking up. But it's perhaps not surprising if Hollywood casting directors have been unsure about what precisely they might do with Pearce. A full quarter of a century into his screen-acting career and we still have no idea what to expect from him. Not many actors can have notched up so many stand-out roles – from the catty young drag artiste in The Adventures Of Priscilla, Queen Of The Desert to the grimy outlaw in The Proposition (Pearce's favourite among his own films) and a mesmerising turn as Andy Warhol in Factory Girl – without acquiring a marketable persona.

In the flesh, the 43-year-old actor, who was born in Ely, Cambridgeshire but moved to Geelong near Melbourne at the age of three, is anything but enigmatic. We meet in the hushed drawing room of a London hotel. Pearce has short, tousled hair, sandpaper stubble and is wearing a tight black sweatshirt and blue jeans. He declines the offer of coffee, saying, "My problem is I'm an addictive personality. I can't have one coffee. I can't eat one piece of chocolate. I can't have a little bit of drugs. Well, these days I can. But I'm just a bit of an extremist." All this before he's been asked a single question.

In 1976, almost six years after Pearce moved to Australia with his parents and older sister Tracey, whom he describes as "intellectually disabled", his father, a test pilot, was killed at work. He says his mother, a no-nonsense teacher from County Durham, did her best to protect him. "But Tracey takes a bit of looking after, and if you see your mum struggling, you've got to help. The combination of that, and Dad being gone, made me take on a level of responsibility that was abnormal for an eight-year-old."

Pearce found solace in pursuits that lent themselves to isolation, such as bodybuilding (he was named Mr Junior Victoria at 16), or that whisked him away from reality, such as acting. But even as a child he had an extreme distaste for the idolatry surrounding showbusiness. "When I was doing theatre aged 12 or 13, I couldn't stand it when people were at the stage door going, 'Oh my God, oh my God.'" He grimaces. "You're allowed to applaud at the end. That's your moment right there. Why does it have to lead on to stalkers, or crazy amounts of fan mail?"

At 18, Pearce landed a regular gig on Neighbours, during the soap's Kylie-and-Jason peak years, and was hit by the full force of fan worship. "I never really enjoyed the fame stuff," he sighs. "Getting chased down the street and all that. A big part of my reluctance comes from having the sister I have. It'd feel wrong standing on a podium going, 'Look at me, aren't I fantastic?' while at the same time knowing Tracey was struggling."

As Detective Leckie in Animal Kingdom, Photograph: Sportsphoto Ltd/Allstar

Post-Neighbours, Pearce has been fortunate enough to work solidly in film, and to land a hit, whether of the commercial or cult variety, every three or four years. But after LA Confidential and the anti-chronological thriller Memento, he made two uncharacteristic detours into the mainstream with The Count Of Monte Cristo and The Time Machine. "I was losing perspective. I was getting myself into big movies in order to get other work. I had been working a lot, getting grumpy with everyone. I was also taking way too many drugs."

Such as? "Smoking pot – other things, too, but mainly that. All day."

Was that a reaction to some deeper discontentment?

"Yeah, I reckon. I had reached my 30s and felt I had the weight of the world on my shoulders. I couldn't walk into a room and be flippant and unaware of what was going on around me. If anyone was struggling, I'd be, like, 'Do they need assistance? Is anyone else noticing this?' I had this crazy sense of responsibility from my childhood, and a pride about fulfilling it, which had turned me into a control freak. The dope wasn't just a response to that. I mean, it's great being stoned. It's a fabulous feeling." He laughs. "But it played its part in making my tolerance of everything go out the window. People would say, 'Good morning' on set and I'd go, 'Fuck off.' I was becoming really unpleasant.

After making four films back to back in 2002, he says he was ready to kill someone. "I needed to get out of the industry. I hated every minute of it, hated everyone. I told my agent: 'Don't call me. Leave me alone.' In that year off, I realised the value of what I was doing. I needed to get away from the stuff I didn't like in order to see the stuff I did." Like many people who've been through innumerable hours of therapy, Pearce talks fluidly about his past psychology. "I'd been acting since I was a kid, you know? And there I was in my 30s doing something that was based on the decision of an eight-year-old. What I had to do was to make the choice as a 30-something to carry on with it."

As Edward VIII in The King’s Speech. Photograph: Rex Features

Now, he seems excited to be riding tall again. His roles in The King's Speech and Animal Kingdom, though fairly small, are vital. In the former, he plays David, aka Edward, Prince of Wales, who abdicated in 1936 to pursue his relationship with Wallis Simpson, leaving the throne to his brother. The story focuses on the friendship between the stammering Bertie (Colin Firth), crowned as George VI, and his speech therapist (Geoffrey Rush), but Pearce introduces colour and volatility to what could be a dutiful film.

"David was complex but also strangely straightforward," Pearce says. "He thrived on enjoyment. He wanted all the things that gave him pleasure, but then he was told he had to be king. And he'd never craved that; he hated that structure. He just decided to do whatever he could to get what he wanted."

He plays an equally pivotal part in Animal Kingdom, based on the real-life warfare between Melbourne cops and a criminal clan. As Leckie, a senior detective coaching a potential witness, he is the moral centre of the film. "Listening to the real interview tapes, there's none of the shouting and slamming the table that you get on American TV," he says. "Just long hours and meticulous detail. 'Now, remind me again, did you say you were at the door after he came in or before? Let me just write that down…'" The film's writer-director, David Michôd, knew the part could be dull in the wrong hands. "All that buttoned-down, almost robotic cop-speak could have just played flat," he says, "but when Guy came on board, I knew it would be compelling. One of his greatest attributes is this ability he has to straddle a number of moral fences. He can play heroes, but he never carries unambiguously heroic qualities."

Pearce thinks the tone of Animal Kingdom – understated where a US equivalent might be hysterical – is specific to Australia. "Our films tend to ask: what's the least amount we can do or show while still making you aware of what's going on?" He agrees it's not a bad description of his own muted acting style, but reflecting on his work seems to frustrate him. "I've gone round and round in circles trying to comprehend it and I can't."

After the disillusionment he experienced in his 30s, which he refers to now as a "mini nervous breakdown", he is clear about what keeps him acting. "I'm interested in the psychological exploration of human nature, and it just happens to come in the form of film-making." His favourite reaction to LA Confidential, in which he played a priggish, uptight cop, was when someone told him, "I fucking hated you in that movie! I couldn't believe I was rooting for you at the end." He grins. "That, to me, is wonderful. I want to play characters who do horrendous things, yet perhaps survive. Or who try their utmost and are whipped away from this world."

Therapy has left him confident that he could handle another professional crisis, if it came along. "That and my fabulous wife." He married Kate Mestitz, a psychologist, in 1997 (it was a big year: he also turned 30 and appeared in LA Confidential). "Kate's so great. I'll complain about something and she'll say, 'Well, that's not mine, that's yours.' I'll be like, 'Right. Right.'" Is she a former control freak, too? He thinks for a second. "Yeah, probably. Sounds like we met through a control freak internet dating service, doesn't it? But things have calmed down. I can walk into a room full of people now and not feel I have to worry about their wellbeing."

• The King's Speech opens on 7 January.