Ewan McGregor is nearly an hour late. But there is no apology when he arrives. Instead, I'm love-bombed with Hollywood charm: diving on to the velvet sofa of the Mayfair Hotel, London, he checks my Dictaphone is running, rearranges our table, pours us glasses of water and throws in a joint cappuccino order for good measure.
An agitated publicist clutching a clipboard hovers. The interview looks close to sliding into the swamp of stage-managed press junkets. Then I mention the riots. "I just thought, fuck off, this is embarrassing," he recalls, hair perfectly parted, but demeanour briefly devoid of charm. While the nation agonised after the events of last August, McGregor took a different view. "I recently worked on a film with Waleed Akhtar, a famous Egyptian actor who had been involved in the protests in Tahrir Square. There you saw social unrest happening for a political reason; an attempt to try and force social change. Here, it was about nothing. It was just people smashing windows of shops and trying on sneakers to make sure they fitted before they stole them. All around the world it was a big embarrassment, with no motivation other than: 'I'm not very happy and I want things – so I'll just take them'."
Plainly such thoughts have been fermenting and catch fire on contact with air. McGregor becomes incensed: "It's probably more of a sign of how good we have it, and how easy things are over here; that people are more concerned with grabbing commercial goods than the way our society is structured."
One might argue that this is all very well for a wealthy, married father of four, who recently moved his family to Los Angeles, California, for a better life. He concedes that life there gives a skewed impression of the rest of the world. I remind him of Sean Connery – one of the few Scottish actors with a greater claim to fame – who once declared himself fed up with "the idiots" in Hollywood and the "ever-widening gap between people who know how to make movies and the people who green-light them". But McGregor will have none of it, insisting film-making is "no longer a nationality-led trait". But he concedes that the "lack of news" in the United States can result in feeling "quite cut off", making it hard to follow – or care much about – current affairs.
Perhaps this is no great loss. He admits to not having taken much of an interest in the recent party conferences. "I don't have a great deal of trust in politicians," he says bluntly. "The rare times I watch football, I'm struck by the bad acting, such as when players throw themselves to the ground when they blatantly haven't been tackled. Cheating has become part of football, and politics is now the same." His older brother's public statements critical of MoD defence cuts – Colin McGregor is an ex-RAF Tornado pilot – are unlikely to have done anything to improve his belief in political leaders of any stripe.
Which leaves the question: what does he believe in? He would be happy if we thought some of the answers to that lurk in Perfect Sense, his new film. Billed as a science fiction love story, it features McGregor as a Glaswegian chef who falls in love with an aloof epidemiologist played by Eva Green, as the world is close to collapse.
"As human beings, falling in love is one of the huge emotional journeys we experience," he says. Barely pausing, he clicks along in Hollywood mode once more: "I have always been interested in romance and exploring it in work. This is a story about two people reluctantly falling in love with each other. I thought it was a clever writer's construct – when we fall in love we lose our senses and here the world is losing its own senses."
The project reunites him with Ewen Bremner ("Spud" from Trainspotting) and director David Mackenzie, whom he first worked with on the impressive Young Adam, an emotionally driven esoteric movie that came out in 2003. But his latest effort, which is peppered with all kinds of hard-to-swallow premises (the apocalypse; a business-as-usual mentality despite disease, global deafness and permeating insanity), asks more questions than it answers.
Here is one of our finest actors, who gave unforgettable performances in Shallow Grave, Moulin Rouge!, and, for the geeks among us, the Star Wars trilogy. Yet in recent years he has featured in some spectacularly underwhelming efforts, and more than one stinker. They include Cassandra's Dream, Woody Allen's flatlining London-based crime comedy; Stormbreaker, the first and last of a planned series of British spy movies; Miss Potter, and Scenes of a Sexual Nature, which one critic dismissed as having only one discernable message: "Hampstead Heath is a nice place to be on a sunny day".
McGregor is smoothness itself on this one, insisting that price tag and star billing do not motivate him. He has five films in the pipeline – each sprinkled with promise – and insists he intends to "take his time" and not be swayed by the eternal quest for the next blockbuster. Looking studiedly earnest, he says: "I approach it as an actor tackling a character. Not a famous person doing the next thing that keeps us famous."
But he finds it hard to mask his annoyance at any suggestion that Trainspotting is his finest hour. It is a sore spot that people will not stop rubbing: last year it was rumoured that he is to reprise his role as Renton in a sequel. For that to happen McGregor would have to bury the hatchet with Danny Boyle, with whom he fell out after Leonardo DiCaprio was given the lead in The Beach. If they are back on terms, McGregor doesn't let on. Hollywood smoothness is pursued by a terse: "Does he say that is happening now?" Boyle, by contrast, was jovial last year when he insisted "it will happen", adding: "It would be a wonderful thing where they've all aged into a mid-life crisis."
By now the publicist is gripping her clipboard so hard her knuckles whiten. A young radio presenter with a comical-sized microphone head is itching to get in the ring. McGregor picks up his cue and slips back into Hollywood business mode, a man in a hurry. But, in case I am in doubt, he punctures any thoughts of a return to the heroin-ridden streets of Edinburgh, insisting he hasn't yet seen any script. "I would be worried of damaging Trainspotting's standing by making a poor sequel," he says. "The film is too important to me and British cinema. If we made a crap sequel, it would be a real shame."
And just as suddenly, I'm shunted to the door.
An actor's life
1971 Born Ewan Gordon McGregor on 31 March in Perth, Scotland.
1989 Attends the Guildhall School of Music and Drama in London.
1994 Comes to wider attention in Shallow Grave, Danny Boyle's directorial debut.
1995 Marries French production designer Eve Mavrakis.
1996 Stars as Renton in Danny Boyle's Trainspotting.
1999 Plays Obi-Wan Kenobi in first of the Star Wars prequels.
2001 Pairs with Nicole Kidman in Moulin Rouge!.
2004 Motorcycles around the world with Charley Boorman in Long Way Round, followed by Long Way Down in 2007.
2005 Takes lead of Sky Masterson in Guys and Dolls in Donmar Warehouse, London.
2007 Plays Iago in Othello at the Donmar Warehouse.
2009 Features with Jim Carrey in I Love You Phillip Morris.
2010 Wins European film award best actor in Roman Polanski's The Ghost.
2011 Takes the role of Dr Fred Jones in Lasse Hallstrom's British comedy Salmon Fishing in the Yemen.