The moustache is unexpected, but then moustaches so often are. This one is blonde and thick as a brush and looks as if it may be concealing a rather stiff upper lip. "It's for a film, Beatrix Potter [with Renée Zellweger]," says Ewan McGregor, fingering the 'tache self-consciously; indeed, the beard that has come to define him of late only came off after our photographer's visit. "It's rather fetching, isn't it? But it is only temporary, as I've a feeling it adds years to me. So once the film is done, that's it, it goes."
We meet at two o'clock on a Friday afternoon in northwest London, at McGregor's local restaurant. The actor has already eaten and so we restrict ourselves to fluids. Not alcohol, though. McGregor hasn't touched a drop for five years now, and for reasons he is unkeen to divulge: "Let's just say it was easier for my life not to drink than to drink." And so we stick to Coke and coffee. No cigarettes either, as he has given those up, too.
He is slighter than he appears on screen, perhaps no taller than five foot nine, his bright blue eyes, which dominate his face, somehow managing to contain both enthusiasm for the task at hand and a wandering distraction.
"For the first time in a long time," he begins, "I've afforded myself some time off. I've done nothing since Christmas except spend time with my wife and kids, fuck around on motorbikes and read through a whole bunch of film scripts. It's been great."
He is surprised, he says, by the quality of scripts on offer, which remind him just what an enviable position he now occupies.
"No two are the same, which is just fantastic for an actor. After Potter [Beatrix, not Harry], I've absolutely no idea what I'll be doing next, but it seems I'm spoilt for choice. And don't think I'm smug about it, because I'm not. I know I'm in a very rare position here, and I'm very grateful ..."
His attention is suddenly distracted by a woman walking past our table, a tiny baby clamped to her shoulder. His eyes grow misty. He already has children, two girls aged 10 and four. I ask him if he'd like any more?
"Oh, absolutely yes," he murmurs, eyes still starry. "More and more and more." He switches back to me. "Anyway, sorry, where were we?"
There was a time when McGregor would rely upon multiple cans of Red Stripe to help him through media commitments: "But that did prompt a certain loss of control over my tongue, shall we say," he grins. "I've been told off because of that on more than one occasion."
One such occasion was from director George Lucas, who took umbrage when McGregor, perhaps a little too loquaciously, admitted that he found the filming of Star Wars: The Phantom Menace (in which he played a young Obi Wan Kenobi) terminally boring.
"But it is!" he reiterates now. "Four months in front of a blue screen [on to which special effects are subsequently added] is incredibly, relentlessly tedious and I defy any actor not to find it so. But that doesn't mean I think Star Wars is crap or that I am crap in it, it's just the process is - well, it's tough."
Lucas was also displeased when the actor went on record to say that he thought The Phantom Menace was a crap title for a film.
He laughs loudly. "What can I say? It is a crap name - but, come on, let's change the subject. I've got into trouble over this before, I don't want to again."
Yesterday, in selected cinemas across the UK, Ewan McGregor's latest film opened. It's called Stay, another of his American efforts, and it is, essentially, that staple of Hollywood output: the psychological thriller. But director Marc Forster, who found success in 2004 with the charming Finding Neverland, clearly wants to be another David Lynch, for his picture is so riddled with visual red herrings that it ultimately ties itself in knots. It is entirely possible to watch the film without having the faintest idea what is going on. McGregor plays Sam Foster, possibly a psychiatrist, perhaps not, who strives to keep a patient of his from committing suicide three days after they first meet. Bob Hoskins is in it, and he is blind. Then he is not. Naomi Watts plays his girlfriend. Or maybe she doesn't. McGregor drifts through much of the action with a confused expression on his face and a hairstyle that looks like it got that way due to a severe electric shock.
For upwards of 20 minutes, we discuss the film's multiple strands and potential meanings, but he doesn't want our conversation reprinted here in order to avoid ruining it for everybody else.
"I think it's open to interpretation," he says, "and that's a good thing, right?"
Not in America, it isn't. It opened over there last year, and bombed.
"It took ages to get a release," he says (Stay was made back in 2003). "There was great debate, I believe, over whether any of it made sense and how it would subsequently be sold. The distributors wanted Marc to re-shoot the ending to make clear what was going on, but he refused. As I understand it, there was a falling out. Anyway, it was eventually released without a fanfare, no premiere, nothing." He shrugs his shoulders. "But, you know, never mind. It doesn't really matter to me whether the films I'm in are successful or not. I do them because I like them, not because of box-office potential. That doesn't mean I don't want them to be successful, because of course I do. I love the buzz you get from being in a really big hit. It's just, with me, that doesn't happen all the time."
Too true. His last film, action thriller The Island, in which he flexed biceps while Scarlett Johansson pouted, also stiffed.
"Yes, but success is not very often a reflection on how good a movie is," he argues. "Great films I've been in haven't necessarily been successful, while some of the terrible ones, curiously, have been."
And which are the terrible ones? He arches his right eyebrow, Roger Moore-style. "You don't think I'm going to answer that, do you?"
The occasional flop notwithstanding, Ewan McGregor is comfortably the leading actor of his generation. Born in Perthshire, Scotland, in 1971, he grew up idolising his uncle, actor Dennis Lawson, and it was his influence that prompted him to pursue his own celluloid dreams. His big break came at just 21 in a TV adaptation of Dennis Potter's Lipstick On Your Collar, but it was Danny Boyle's directorial debut, Shallow Grave, a year later, that announced his arrival in showboating style.
"An amazing film," says its star, "I loved it. The film was well received, just as I knew it would be, and I thought to myself: of course it's well received! Yes! I've arrived! Give me more!"
Art-house pretension followed soon after - McGregor naked and tattooed in Peter Greenaway's The Pillow Book - but it was Boyle's second film, Trainspotting, that would f launch the young actor's career like a skyrocket. In it, he played Renton, a heroin addict desperate to kick the habit and leave his past behind. The film was a phenomenon, his lead performance revelatory: here was someone who oozed not just a garrulous charisma, but towering confidence as well. You watch Trainspotting and you sense that McGregor doesn't merely know he is good, but that we all know it, too.
"I suppose I was guilty of arrogance back then. That would be a fair reading of the situation, yes," he laughs. "With Trainspotting becoming huge, I just felt that everything was going terribly according to plan. It was an absolutely amazing time. I was 23, 24. Trainspotting was defining a generation, Britpop was everywhere - Blur, Oasis - I was making films with my friends and we were being showered with acclaim. I felt like a rock star; I didn't want it to stop. It was one film after another back then, three or four a year for five years, working flat out. I fell in love with Eve at the same time, we had Clara, we got married, bought a flat ..." He looks straight at me, eyes huge. "A fast time, furiously fast, and really and totally fucking great."
It wasn't all plain sailing, though. After another Boyle collaboration, A Life Less Ordinary in 1997 (a film which had its faults but a wonderful effervescence nevertheless), he was then overlooked for the director's next project, The Beach. When the lead role went instead to Leonardo Di Caprio, the Scotsman was furious. He felt he'd been done over by a mate, and subsequently spoke of his sourness to anyone who asked.
Last year, they bumped into one another in a restaurant, "and, yes, we hugged and it was good to see him because I do miss him. I loved nothing more than working with Danny; he brought out the best in me, he really did. The man is a phenomenal talent."
And so were bridges rebuilt and friendships restored? His gaze dips; colour comes rapidly to his cheeks.
"No, no we're not. We still don't speak to each other, and that's a shame. A real shame."
Arguably, though, he doesn't much need him anymore. While it is probably true to say that he has never quite impressed in a film the way he did under the aegis of Danny Boyle, McGregor has nevertheless established himself as a wildly eclectic performer, thriving in all kinds of genres. There have been musicals (Moulin Rouge), gritty dramas (Young Adam) and flights of pastel-coloured fantasy (Big Fish). However, his more recent choices (Down With Love, The Island and the much maligned Star Wars trilogy) suggest, to some at least, that he is motivated more by money these days than art. Rubbish, replies McGregor.
"I've never done a film just for the money, no, but that doesn't mean I don't try to get paid as much as I possibly can for them, because I do." He points out that the responsibility that comes with having a family does require certain financial stability. "But I am reasonable. If I'm doing a small British independent movie with a £2m budget, I'm not going to claim half of that just for myself, am I? But if it's an American movie with a $100m budget then, yes, I'd want a good slice of that. Ultimately, I make my choices because I find something interesting in each film, and that doesn't matter if it's earnest and worthy like Young Adam, or a big action yarn like The Island. Everything I've done, I've taken something from. I've learned, and you grow by learning, don't you?"
For six months last year, McGregor played Sky Masterson in the West End musical Guys and Dolls. Critics thought that this was a considerable risk for such an established screen actor, one that could only end in embarrassment. Instead, the play was a smash hit, McGregor receiving a Best Actor nomination in this month's Olivier Awards. It was, he tells me, one of the best things he has ever done.
"An absolute blast, a brilliant, wonderful time. I'd longed to be on stage again and surrounded by a company of actors. Five weeks in a rehearsal room with these amazing people was almost as enjoyable for me as the actual performances. It was the perfect antidote to films as well, because it keeps you fresh."
And the theatre was itself an antidote to what he had done before that, a four-month trek around the world by motorbike with his friend, actor Charley Boorman, which was immortalised on film for the benefit of a Sky TV documentary called The Long Way Round. McGregor loves his motorbikes, but more than that, he loved being away from it all, from the pressures of everyday life. Twelve hours a day with his head under a motorcycle helmet, he says, gives you a lot of time for contemplation. It's effectively self-therapy.
"You have time to think about everything: life, old girlfriends, the universe, work, your family, everything. I found it all tremendously therapeutic."
He and Boorman are now planning to do it all again next year, this time from John O'Groats to Cape Town. Does this mean, perhaps, that he is in continual need of self-therapy?
"No, of course not, that's not what I'm saying. It's fun, basically, really terrific fun, and the people you meet are just amazing. But I won't lie, I definitely use the time to work out all manner of things."
One of the "things" he will happily admit needs his contemplation is his attitude to fame. The constant tabloid speculation of dalliances with his female leads - Nicole Kidman, Cameron Diaz, Scarlett Johansson - affects him bitterly.
"Does it hurt? Of course it fucking hurts. To see lies written about you hurts a hell of a lot, which is why I now avoid reading the papers altogether. My wife is totally cool about it, she doesn't care anymore, she laughs it off, and I'm trying to live by that example, but it's difficult. It's particularly difficult when the papers print pictures of my children. I won't have that."
He tells me that on the few occasions photographs of his daughters have been published in newspapers, he has sued over it - sued, and won, which, he says, "sends out a very strong signal not to fucking do it again".
Gradually, the bile that has come out of nowhere begins to settle, and he smiles in apology. "But anyway, who wants to hear somebody very comfortably off in life bitch and moan, eh? Listen, I need to be somewhere else now, but wait there." He nips back to his house to fetch a copy of The Long Way Round on DVD, and presents it to me with almost paternal pride. "Hope you like it," he beams. The smile broadens and the moustache lifts, the stiff upper lip conspicuous by its absence.
'Stay' is on release nationwide