Peter Mullan and Billy Boyd plunge into icey waters in On A Clear Day
On and off-screen the 45-year-old is a formidable presence, he has a concentrated energy that seems to come off him in waves - the kind of verve that suits his On A Clear Day character perfectly.
Mullan plays Frank, a Glasgow dockyard worker who, devastated by redundancy, finds a new way to channel his efforts - quite literally. His abrasive attitude has alienated his son and, in an effort to rediscover his self-esteem, he decides to train to swim to France.
The role was certainly a physical challenge for Mullan, who spent almost six months in training, which was something of a mixed blessing.
"I did a mile every day, six days a week," he says. "It was mentally boring for the first three months especially, then I got a bit more used to it... I'm still doing it so it can't have been that bad."
"To be honest, I wish I had known 20 years ago how much of a de-stresser it was. It's actually difficult to become anxious. There's something about swimming, that, despite yourself, you chill. Takes out all that s**t that you carry around with you all the time and that's why I've kept it up."
Even with a stunt double, shooting the film required a lot of time in the water - much of it cold. Chunks of the movie were shot in the Irish Sea which meant the actors had to hop in and out of the water to shoot, to make sure they didn't get so cold they couldn't work. But despite the shivering swims, Mullan is pleased that the chill factor is carried over in to the finished film.
"I knew it was going to be cold but I hadn't realised how quickly it crushes you and how difficult it is to breathe - every stroke felt like you'd swum a mile.
"The thing is, cold doesn't always 'read' on a screen. It is the one thing that is really difficult to get across. You can get across heat much easier but cold is difficult because the audience is always double guessing you. So they are assuming that if there is no landmark, that it's just water.
"Quite rightly, they assume that you're in a water tank or you're in Hawaii - warm water. The shots I really liked were when the water was as I remembered it - a blacky-blue colour. And it looked cold. I prefer the really freezing-looking shots, so people know what I f***ing went through."
On A Clear Day may have chilly water, but its message is a warm one. Triumph in the face of adversity is the order of the day as screenwriter Alex Rose revisits the paths trodden by other recent British films, such as Calendar Girls, Brassed Off and The Full Monty. But Mullan argues that mainstream is where it's at - it's just that a lot of independent film-makers haven't caught on yet.
"Those of us on the left, socially conscious type of cinema need to start playing with form, genres and style," he says. "Otherwise you just get trapped in a kind of worthy social realism and because the sentiment is good it's like 'it doesn't matter how we present it to you... it's the thought it counts'.
"But we need to grow up, guys. I don't want to abandon the multiplexes to some of the nazi-type of stuff you get there and then let film festivals go, 'Yeah, we get the more humanitarian left-orientated part of cinema'.
"My family don't tend to watch arthouse types of film, festivals or whatever - they go to UG f***ing C. I'm not just going to walk away from my family, my class, my friends because 'I don't go there'.
"I want to be in there with films that hopefully aren't compromised and hopefully have something to try to touch upon. I go to the cinema a lot with my kids. You look up and, man, there's virtually nothing I want to see. Sometimes I even look forward to the fact that I'm going to see a kids' movie."
The state of modern cinema isn't the only thing that Mullan feels strongly about, he thinks that television has lost its way, too, arguing that it is dumbing down at just the wrong time.
"It's actually the very very young who go to the cinema. That's why programmes like Six Feet Under and the Sopranos caught the TV industry by surprise, because just as we in the UK were dumbing it down, because producers thought there was a young audience, the Americans realised there's a huge 30 to 60-year-old audience who've got out of the habit of going to the cinema and the theatre but want to see stuff.
"I think the so-called British TV is at it's poorest that I can remember. I really think they've completely misjudged who their audience is. The youngsters are going to the cinema, it's guys like me sitting there at home watching that crap."
He may not get out to the cinema much but Mullan is certainly appearing at it more and more. With so many strings to his bow - on both sides of the Atlantic - it must be tricky to decide whether to write, direct or act next. But he is certainly fired up about the possibility of putting pen to paper.
"I'm annoyed with myself because I wanted to have a script by the end of last year and it never happened for a variety of reasons. So I am determined now."
However, he refuses to be drawn on the subject matter. "I was working on so many different ones that's why I blew it," he says. "I kept jumping from one script to another because I had about 29 ideas all fairly well figured out. I kept jumping because I hadn't decided which one to go for and that was silly on my part.
"It's four years of your life, so you have to choose the right one. Not necessarily the one that will work, because you never know what will work. But the one you can live with for the rest of your days but, particularly in the short-term, the one you can live with for four years."
On A Clear Day and his latest film Cargo - which he describes as "a cross genre film with horror and a social conscience" - are certain to see Mullan's acting talents in greater demand than ever, so let's hope four years is all we have to wait.
On a Clear Day premieres at the Edinburgh International Film Festival on August 20.
