Sam Riley: the beat goes on…

In 1957 Jack Kerouac, suddenly famous as the authentic prophet of the Beat generation, wrote to Marlon Brando to ask him to star in a film adaptation of his novel On the Road. The instantly legendary book, written in three weeks on a single roll of paper, had just been published to contentious acclaim, and Kerouac, never a man scared to dream, had high hopes that the film could be a similar fast-forward phenomenon. He imagined himself starring in it as his questing alter ego Sal Paradise, alongside Brando, who would take the part of Dean Moriarty, the fictional version of his Benzedrine-fuelled soulmate, Neal Cassady.

In his suitably breathless letter to Brando, Kerouac could hardly contain his excitement at the prospect: "I'm praying that you'll buy ON THE ROAD and make a movie of it… " he wrote. "Don't worry about the structure, I know to compress and re-arrange the plot a bit to give a perfectly acceptable movie-type structure… I visualise the beautiful shots with the camera on the front seat of the car showing the road (day and night) unwinding into the windshield, as Sal and Dean yak… You play Dean and I'll play Sal (Warner Bros mentioned I play Sal) and I'll show you how Dean acts in real life… we can go visit him in Frisco, or have him come down to LA. [He's] still a real frantic cat… All I want out of this is to be able to establish myself and my mother a trust fund for life, so I can really go roaming around the world… to write what comes out of my head and free to feed my buddies when they're hungry… "

Brando never replied to Kerouac's letter, though he kept it (it sold early this year at auction for $33,600), and the movie of On the Road was often dreamed of but never made by the time Kerouac had drunk himself to oblivion aged 47 in 1969. A young director called Francis Ford Coppola picked up the rights, and in the subsequent 40 years at least five versions of a script were worked and reworked, and almost every up-and-coming actor with a restless soul and an eye for the horizon was linked with the mythological project – from Dennis Hopper through to Sean Penn. Though the book was the prototype of a hundred road movies and one blueprint for "bromances" from Butch Cassidy to Brokeback Mountain, it seemed ever more resistant to adaptation as the decades rolled on. Jean-Luc Godard had come close to directing it as his first Hollywood film; by the time the Brazilian director Walter Salles approached Coppola with the ambition to do it in 2007, the original travelling-light encounter with the American road was freighted with all sorts of baggage.

In homage to that fact, before he made the film, and while production money ebbed and flowed, Salles, the director of the Motorcycle Diaries of Che Guevara, made a documentary about the journey Kerouac's book itself had undergone on the way to the cinema screen. One of the first things Salles did when he had finally cast his Sal and Dean was to show them this movie at a month-long total immersion "beatnik bootcamp" in Montreal, preparing them for the months of filming ahead. I'm sitting in a hotel in London with Salles's Sal Paradise, listening to him recount some of that history, and the surprise is that he is doing so in a thick Yorkshire accent.

Sam Riley, who relishes the accent in question, could never be accused of ducking a challenge. His first screen role was as the ultimate doomed and cultish rock star, Ian Curtis of Joy Division, who took his own life in 1980 and whose fans had the fervour of disciples. It was Riley's mesmerising performance channelling the singer in Anton Corbijn's film Control that convinced Salles he could take on the even more daunting legend of Kerouac. In between times Riley had also set himself up to fail as Pinkie Brown in Graham Greene's Brighton Rock, a remake of the 1947 film which was the benchmark of postwar British cinema.

"On the Road is another one of those," Riley says in his cheerfully blunt way, as if it is his fate to play the unplayable, "a film in which the audience has a very clear idea of who they think your character is, so you know you are asking for it. But that's the challenge. And that's why you know you don't want anyone else to do it. I auditioned for Sal Paradise early in 2009 and it seemed to go well, but I didn't hear anything for 18 months – and part of me was a bit relieved, to be honest – but then my agent called and said: 'You start filming in a few weeks' and I thought: 'Fuck, here we go… ' Walter showing us the documentary he had made didn't help much. He had footage of a lot of Coppola's casting sessions from over the years. The young Russell Crowe and Matthew McConaughey and others. Brad Pitt saying he was glad he eventually got too old to play Sal because it would have been too much pressure. I was thinking: 'Great… '"

At his hippy retreat Salles had Riley and Minnesota-born Garrett Hedlund, who would play Dean, meet everyone he could find who had known the original Beat double act, writers and drug casualties and people who had been around their San Francisco of the 50s. Neal Cassady's son came for a weekend. And all of these survivors looked Riley up and down. "Obviously I was as surprised as anyone else that Walter wanted a Yorkshireman to play Jack Kerouac," he recalls. "I remember the first biographer we met, a very nice gentleman whose whole life revolved around academic study of the Beats. Garrett and I greeted him at the door and he said to Garrett: 'You must be Dean.' Then looked over my shoulder and said: 'Which one is playing Kerouac?' I said: 'I am.' He said: 'You are awful tall to be Kerouac, and you don't have blue eyes.' And I started to say something else and he said: 'My God! Are you British?'"

Not surprisingly, after a month of this, Riley and Heglund, and their co-star Kristen Stewart, who plays Dean's wild-child girlfriend, Marylou, were desperately keen to move on. Which was probably Salles's intention. Over the subsequent six months they properly took to the highway. "Walter wanted us to be as bonded as possible. We had to wrap Kristen's stuff in the first three months so we were flying all over the place to get the right weather," Riley recalls. "We went down to Patagonia for four days for the snow, and then Louisiana, 100% humidity, then Arizona, then Mexico, then Calgary, then we finished in San Francisco… "

I'd watched the film a couple of days before seeing Riley. That sense of ever-shifting location is its abiding character, along with the diminishing highs of drifting and home-wrecking as Sal and Dean search for their personal nirvanas in sex and drugs and writing and change. Riley and Hedlund and Stewart make a mythical threesome (sometimes in every sense), but the yearning for newness that gave the book its tone, that made it the attention-deficit bible for generations of rootless young men everywhere, is predictably tough to replicate on screen. The sadness of always chasing one last good time quickly becomes repetitive, which is part of the point. After a while only the scenery changes, though there are plenty of memorable characters along the way, notably Viggo Mortensen's William Burroughs.

It is a testament to Riley and Heglund that Sal and Dean's complicated love for each other is likably credible throughout. It couldn't have worked had he not got on well with Hedlund, Riley says. "It was a big ask in that way. Six months travelling together. We couldn't have grown up in more different parts of the world or come from more different backgrounds. But Garrett's not a typical young actor; he's very warm. He was already in character when I met him two years before. It was the part he was born to play, really. He's more considerate than Dean, but all the talking in mad obsessive tangents was completely him. I remember the first morning – he came in with this poem. He was like: 'I was up late last night and I've written something and I want to share it with you all.' And he read out this amazing poem. I thought: 'Bastard.' And I could see Walter looking at me thinking: 'What have you got?' I was like: 'The dog ate mine, you know... '"

I'm guessing that the film may have cured any vestigial wanderlust in 32-year-old Riley; it looks like the kind of job that makes you happy to get home.

He laughs. "It's odd. I was cured of that already by being in my band." In his early 20s, having left his public boarding school, Uppingham, and having been rejected by all the London drama schools, Riley fronted a band called 10,000 Things, in which his brother played bass. They threatened success for a while, playing the Reading Festival, supporting Razorlight and Babyshambles on tour, but it came to nothing in the end. It did in retrospect, though, give Riley some insight into Kerouac's vagabond spirit.

What was the furthest they got, I wonder.

"We went all the way to Dundee once, which was a long way in our bus," he says. "We'd bought it from Leeds council and it only had a seat at the front. We had sofas and stuff in the back, mirrored windows. We loved it. In a different town every night. It was great for a while."

At school Riley had told people who asked that he would either be a rock star or an actor, "not being cocky, only because acting and singing were the only things I could do". It was a while coming. The first time he ever saw himself on a screen was the premiere of Control at Cannes five years ago. "I was lucky it was such a beautiful film," he says. "But it was very weird. I mean like hearing your own voice on an answerphone, but magnified a lot. I think I left nail marks in the arms of the seat. You just fear you are going to do something false. You are just thinking: 'Don't fuck up.' And as an actor I still don't really know exactly what I am doing most of the time." You wouldn't guess; his debut won him several awards, including the unofficial accolade of Mark Kermode's actor of the year, but his experience remains limited.

He's still only properly been in four films, which makes it a bit like a high-wire act, he suggests. He is grateful for the advice of his wife, Alexandra Maria Lara, whom he met working on Control – she has been a star in Germany and beyond since she was 16 and was Oscar nominated for her role as Hitler's secretary in Downfall. They live in Berlin, which Riley loves. "You know, you set out wanting to be as famous as you can be, but then the closer it gets, you get a bit apprehensive," he says. He had seen the price of fame up close in brushes with the likes of Pete Doherty, and he could mine some of that experience for the Kerouac film. "I feel quite safe and isolated in Germany," Riley says. "My wife is very well known there. But I am only looked at when I am holding her hand."

It allows him to maintain his inner Yorkshireman even, as he mentions in passing, now he is working with Angelina Jolie on the Disney film Maleficent. "My parents are relieved as much as anything that I'm getting some work," he says with a smile. "They get to visit me on set. I was driving them around Pinewood on a golf buggy. They met Angie. They loved all that. My father is a typical Yorkshireman. When I was about 12 the whole family went to Disneyland – it was our one real big holiday abroad. So he likes the fact Disney is now paying me. 'Sam, you realise that was like a free holiday now,' he told me."

As the mother-fixated Kerouac discovered perhaps too late, however hard you try, you can never properly escape where you came from. Riley rather enjoys that fact. "I caught myself looking at the thermometer outside the house the other day," he says. "To see whether it was warmer than yesterday. I thought: 'Christ, it's happening. I'm becoming my dad.' I'll be getting the map out next and seeing exactly where we drove to in On the Road."

On the Road opens on 12 October