Trocchi's 1954 cult novel is written in the first person, but Mackenzie rejects the obvious solution of giving his anti-hero, Joe Taylor, a doomy noirish voiceover. Instead Joe's affectless state of mind is expressed through the gritty visual texture and cold, grey-blue palette, flat, detached dialogue and above all Ewan McGregor's performance. Paring away the streetwise perkiness of his earlier roles, he evinces a hungry, raw dissatisfaction, his mouth skewed in a grimace of anticipated distaste.

Film 2003: What's the movie about?

Ewan McGregor: Trocchi wrote the book in the 1950s, "Young Adam" is about a man on the outside of society. Trocchi was very much a man outside society, he was a heroin addict and a pornographer. A very interesting character. It's quite dark, it's very erotic, and it's a very adult film. I feel at the moment we're getting movies that over explain themselves to us, to the point that you come away feeling stupid. This doesn't do that, so as actors we get the chance to play and let the audience decide, which is lovely.

Do you happily flip between Hollywood films and smaller films like this?

I have had a run of big films, like "Moulin Rouge", "Star Wars", "Black Hawk Down", and I was dying to do a small scale film, where you know all the crew. On big films there's maybe 500 people on the crew and you don't know who half of them are. You can end up feeling as if you're being wheeled on to do your bit and wheeled back to your trailer. On a film like this you're surrounded by people you know, you are all working together to make a film and it's a good feeling. But more than anything, this is a cracking script.

Is it important for an actor of your standing to do smaller films?

I certainly wouldn't say it's your duty or anything like that. I have always been most interested in stories more than anything else and I hope that never changes. It's good for you to do different kinds of work, it makes me happy to do big films and smaller films. This is quite a difficult part to play but if you are constantly playing things you know you can do it is going to take the edge off things and everything will become more mundane.

There was a story you had taken an unscheduled dunking in the River Clyde...

That's a complete myth! My folks were in New York and someone came up and said "How is your son, he's fallen in the Clyde" - and I didn't! I did after that but I was meant to... Peter Mullan got an injury to his back which held us up for a couple of days. I might be a jinx - Nicole's ribs, Peter's back... other actors should be afraid to work with me I think!

How did you get involved with "Young Adam"?

I was sent the script and I thought it was one of the best things I'd read in a long time. It was a blinding script and due to its lack of dialogue - it's very sparse - it struck me as very different and brave.

This is the inevitable sex question. There have been quite a few sexually explicit films in your career. What's the appeal of that? Is it just the stories?

Yeah, it's just that... This story is about a guy who uses sex to kind of fill a gap, I suppose. I don't know exactly what he's doing. There's a lot of it going on in life, so there's a lot of it going on in the cinema, I think. I think if it reflects life, it's got to be in there.

So you're not contractually obliged to get your tackle out in every film?

No, no I'm not, no, but I just think... when people are naked it tells you a lot about their relationships.

Why did you get into acting in the first place?

Er, I've got no idea. I think because I loved old movies, I loved old black and white movies and my uncle [Denis Lawson] was an actor, so he kind of paved the way if you like. He came from a small town that I came from in Scotland [Crieff], so the possibility of becoming one wasn't so unbelievable because he'd already done it. In many ways he paved the way. It's just always what I've wanted to do, since I was nine or something.

How did you get started?

I played music all through school and I kind of performed that way. Then I left school at 16 and worked in Perth Repertory Theatre, which was quite nearby where I lived. And I worked there for about six or seven months, as part of the stage crew. From there I did a one year theatre acting course in Fife, and then three years of drama school in London. I left halfway through my third year to start Lipstick On Your Collar, which was the first thing I ever did.

Were your family supportive of you moving into acting?

Yeah, absolutely. I'm sure it's not great fun for them, or for any parent, when their child says they want to be an actor, 'cos it's quite an uncertain business and it can be terribly hard for most actors. But I just... I never imagined it wouldn't work out for me. I had that absolute certainty in myself that has seen me through, I think, and my parents were absolutely behind me all the way.

A lot of parents tell their children that if they want to be an actor, that's fine, but they should do something else first, so they've got something to fall back on. It doesn't work like that, as far as I'm concerned. It certainly wouldn't have worked out for me. It's important, that spirit of youth, and when you're 16 that can get you kickstarted.

If you're suddenly doing something you don't want to do for four years, just so you've got something to fall back on, by the time you come out you don't have that 16-year-old drive any more and you'll spend your life doing something you never wanted to do in the first place.

So, maybe that's a good thing for parents to encourage their children to do. I personally don't think so. Encourage your kids to spend a life doing something they don't like? That's a bit ****house isn't it?