James McAvoy

James McAvoy’s eyes are sunk deep into his skull, each one looking as if it’s carrying the burden of terrible news. His skin is yellowed, like a smoker’s ceiling, with wrinkles around his eyes. His unkempt reddish beard resembles an ageing Irish setter’s coat. It’s safe to say he’s looked better.

Much of this, it has to be said, is down to the make-up department on his latest film – the set of which, a make believe police station in a tatty Stirling council building, he’s on. But I wouldn’t be surprised if a wet wipe revealed some very real bags under those eyes.

Because not only is McAvoy part way through 35 consecutive days of filming in the miserable winter of 2011, he’s also taking on one of the most distressing roles of his career. He’s playing Detective Sergeant Bruce Robertson: the boozing, snorting, whoring, cuckolding misanthrope of Irvine Welsh’s novel, Filth. He’s the bendiest of bent coppers, with the kind of moral fibre that’d give you the runs for a week. Being Bruce is bound to rub off on you.

“It’s dark as f*cking darkness this film, and I’ve already come away going, ‘F*cking hell, I’m not sure how I’m going to stick this,’” says McAvoy. “One of the scenes was a bit disturbing, and the rest is what’s happening inside his mind. A couple of days I’ve come away quite jangled. I’m not a f*cking method actor, but you do take home an element of ‘what the f*ck have I just pretended to do?’ Because you pretend and pretend and it does get you. Don’t worry, I’m not having a mental breakdown.”

The same can’t be said of Bruce. He may be a git, but he’s also a man spiralling down a psychological helter-skelter. If you’ve read the book, you’ll know that Welsh utilises some very peculiar devices to illustrate that descent, including a monologue from a tapeworm in Bruce’s body. Such devices led to the book being classified ‘un-filmable’, but director Jon Baird, a fellow Scot, has put paid to that claim with an ingenious screenplay; one so far removed that neither Baird nor Welsh wanted McAvoy to read the novel.

“This is my f*cking get-out clause,” McAvoy pleads. “I’m an avid Welsh fan, but he and Jon both asked me not to read the book, which I found quite worrying. But then I’ve had experience of that working out. The writer and director of The Last King Of Scotland asked me not to read the book, just because it’s so different.”

Filthy business

Nearly two years later, we meet again, this time in more salubrious surroundings: the restaurant of London’s Soho Hotel. And it’s not just the building that looks better. McAvoy is clean shaven and neatly coiffured, despite having just removed his motorbike helmet. He’s off to Berlin later, to promote Filth because he “f*cking loves it”, and wants to avoid the traffic near Heathrow. Like Baird and Welsh, he’s committed to getting this film seen. And so he might; it’s something of a masterpiece. He might also be happy that they’ve let him read the book, at last.

“It was a bit hard to read it, actually, just because I’d lived it so long,” the 34-year-old actor says. “Reading bits I didn’t know was quite weird, I didn’t like it. I liked the book, but I didn’t enjoy reading it. I felt too close to it.”

We’re in a pertinent location. It was in this hotel, about 20 yards from where we’re sat, that McAvoy first met with Welsh and Baird to discuss the film. McAvoy claims that it wasn’t a case of trying to sell himself, despite concerns that he was too young to play Bruce.

“Aye,” he says, waving over his left shoulder. “In that room over there. I still remember the meeting. I wanted to do it, don’t get me wrong, but if I hadn’t got it I wouldn’t have cried over it. But I did want to explore mental health in a way that wasn’t just harrowing and ended up with somebody cutting their wrists in a f*cking bath. Mental health is something that gets represented as very gritty. Don’t get me wrong, this film is really f*cking gritty, but it’s got an energy and it’s got a sense of humour that I think comes with insanity.”

It certainly has got a sense of humour. Filth is, without doubt, a comedy – and a very funny one. Bruce is like an extreme Edmund Blackadder; a self-centred bully and manipulator, but one who inflicts cruelty with a blend of style and tragedy that means you can’t help but laugh, almost warm to him. He even has a Baldrick in Clifford Blades, played by Eddie Marsan; an accountant and fellow Freemason who Bruce uses for cash, sport and the aforementioned cuckolding.

“Blackadder is a really good parallel,” agrees McAvoy. “The idea of somebody who’s not as clever as they think they are. Bruce thinks he’s a Machiavellian f*cking genius and he’s really not, and it’s kind of funny watching someone who’s so much less than they think they are try to orchestrate all these amazing ploys and schemes that are really f*cking banal.”

Filth is McAvoy’s best performance to date. Beginning as a cocksure rake, playing his colleagues against each other in a race for a vacant detective inspector position at Edinburgh’s ‘Lothian Constabulary’, he then begins to unravel Bruce and we see a broken man held together by fantasy and denial. As this happens, McAvoy bounces, faster and faster, between emotions like a manic pinball, switching from vulnerable to joyful to vindictive. It’s all in the eyes; from puppy dog to hellhound in a fraction of a second. I ask if it’s something he practises in the mirror.

“No, but when I was a kid I used to sit by the mirror and see if I could make myself cry,” he says. “And I used to fantasise about going to a different town, being a new kid in a new school, and possibly come across a girl who’s getting bullied, and I stop her getting bullied and then she falls in love with me and then we have lots of sex.

“But I’ve not done that as an adult. Weirdly, there’s one line that I say to myself a lot in whatever character I’m playing, when I’m having a pee. When I’m having a pee is my most reflective moment. The line is, ‘You can’t make me do that, you can’t make me do that.’ I don’t know why that is.”

Dark matter

I remind him of things that Baird did make him do, and the scenes that left him “jangled” in Stirling. That day he didn’t want to talk about specifics, but now, less jangled, he’s happy to open up.

“There was a scene where I had to make a 15-year-old girl give me a blow-job,” he says. “She wasn’t 15, she was like 20, but she looked bloody 15. I didn’t want to shy away from any f*cking harrowing bad sh*t that Bruce does, and that’s why I love the script, but in that moment I was like, ‘This is f*cking dark, man,’ and that left me a bit upset.

“The weird thing is, it’s not the scenes that really got to me, it was when Jon let me riff. I riffed more prolifically and articulately with Bruce than any other character. And that was really disturbing, because you riff dark sh*t, and the sense of humour got darker and darker. I have a dark sense of humour, but with Bruce’s humour, which is violent, towards himself, towards others, that left me most jangled. Some piece of dark sh*t comes out, a piece of dark comic poetry, and you’re like, ‘I cannae believe I’m saying this – and enjoying it.’”

McAvoy admits that “not every character you play is that different from yourself”, which, in Bruce’s case, is very worrying. But when I ask him about the moments that make him want to be a bastard, I realise that it probably didn’t require a deep-sea drill to tap into his seam of darkness.

“As a dad,” he says, shifting forward in his seat with a devilish look on his face, “when kids are being bullies in the playground, you can’t smack someone else’s kid and you can’t go up to their parents, because generally they just go, ‘I’m just glad it’s not my kid getting hit.’ So my plan, my fantasy, is to go up to the kid and be like, ‘Hey, where’s your daddy?’ and they’ll point out their daddy, and I’ll go ‘I’m gonna f*cking kill your dad, I’m gonna f*cking kill him if you carry on like that.’ That’s my fantasy. I wouldn’t do it. But I might. I have a lot of dark fantasies, actually.”Cue enormous grin from McAvoy.

Sick boy

McAvoy’s investment in Bruce wasn’t just mental (and I mean that in more than one sense). It may not match Tom Cruise in the ‘doing your own stunts’ stakes, but he gave his physical all to the role as well, revealing a talent that has been lost to cutting-room floors – until now. Two scenes – one in which Bruce lets out a nauseating fart and one in which he vomits in a car – were not done with special effects or animatronic anuses. They were bona fide McAvoy expulsions.

“I don’t remember the fart, but Jon tells me I farted for real,” he says.“I definitely know I’ve got it in me to try. But I’ve vomited in like four movies, and this is the only time they haven’t cut it out, so I’m really glad. I have a very sensitive gag reflex. You’ve just got to think about the things that make you feel sick, start to open your throat a little bit, and about five or 10 minutes later you feel sick. No fingers needed. On Filth, I’d had a lot of orange juice beforehand, because I wanted it to look like that yellowy stomach lining.”

Perhaps it’s this dedication to his work that has kept McAvoy’s star rising, as well as his stomach’s contents. This has been his biggest year to date. Filth is his third cinematic release in just over six months, following Welcome To

The Punch and Danny Boyle’s Trance. Filming has just completed on X-Men: Days Of Future Past, where he went head-to-head with ‘old Charles Xavier’ Patrick Stewart (“It felt almost like an affront, like, ‘That’s how I f*cking do it mate! Come on, give me your f*cking Charles!”), and he’s appeared in a stage version of Macbeth. He’s also just signed up to play Victor von Frankenstein opposite Daniel Radcliffe’s Igor.

The increased profile is unlikely to change McAvoy. He keeps his private life private, particularly when it comes to his family – wife Anne-Marie Duff, whom he met on Shameless, and their young son – the antithesis of the fame-hungry, glamour-seeking actor. He likens the tell-all style of some interviewees to a one-night stand – giving everything up only to lose respect in the morning – and makes the point that it’s easier to believe an actor in a role if they haven’t publicly professed to “loving Made In Chelsea”.

But you’d still expect the critical acclaim, the adulation, to go to even the most level of heads. I ask if he’s ever had a ‘don’t you know who I am?’ moment.

“I’ve thought to myself, ‘You definitely don’t know who the f*ck I am,’” he laughs. “I’ve had that. ‘Oi, Ewan! Ewan!’ I bought a bike from a guy who came out with [adopts cockney accent], ‘So is it true that when Ewan McGregor turns down a part, that’s when you get offered one?’ And it’s like, you f*cking prick. But hey, there are worse things than getting Ewan’s sloppy seconds.”

Filth is at cinemas nationwide from 4 October

(Photography: Perou)