Your dreams of rapping superstardom are stymied by your Scottish sound, so what do you do? Simple: reinvent yourself as a West Coast wild boy, with American accent and history to match. But, Gavin Bain tells Decca Aitkenhead, keeping it up for two years is murder

Silibil'n'Brains commandeered the stage with the swagger of Americans who considered the audition beneath them. It was 2003 and the rappers were making their London debut at an industry showcase for unsigned talent. Freestyling in rhyme, the pair tore through their routine - part Eminem, part skater-boy punk - ripping off T-shirts to reveal lacy bras before leaping into the crowd. In a line-up stiff with tepid R&B acts, the Californians couldn't fail to steal the show. An A&R man in the audience from Island Records wanted to see them the very next day.

Brains - aka Gavin Bain - still feels his heart race when he describes Island's office full of A&R men the following day. "We go round everyone in the room, taking the piss, and they're all like, uh-oh, what are these crazy American kids going to do now?" The pair tease an overweight executive about his girth, and when a member of the boy band Busted walks by, they mock his songs and advise him to shave his monobrow. "And everyone laughs! We're rapping to the point where we don't even know what the fuck's coming out of our mouths, but people are just, like, laughing, loving everything we do."

When the fantasy of a lifetime becomes real before one's very eyes, it can have the strange weightless clarity of a dream. Bain watched an A&R man pick up his phone and start calling management companies to tell them about the hot new West Coast rappers they had to meet.

"These guys," Bain heard him say, "these guys are the real deal."

Within weeks, the pair had signed a deal with a premier management company. Within months, they had signed a record deal with Sony. They headlined small festivals, played Brixton Academy, toured with Eminem, appeared on MTV, partied with Madonna, and got paid more than £150,000.

Only, they were not the real deal at all. They were two Scottish college kids from Dundee, with fake American accents.

I first meet Bain in his lunch hour, in a north London suburb near the watch designer's office where he now works. His look is knowingly urban - directional blond hair, loosely layered skatewear - but his demeanour is diffident, even meek. His decision to out himself as a Scot had been reached only a few months earlier, and he still doesn't seem entirely comfortable in his new - or rather, old - skin.

I'm still not sure if Bain considers his story a confession or a boast. I think he is in two minds himself. Most of the friends and family I meet err towards pride in his epic pretence - and maybe regret that the act came to an end. But the legacy of living a lie has not been easy for Bain, he will readily admit. Now that he's no longer keeping a secret, he can't stop wondering what everyone else must be hiding, and has trouble believing a word anyone says. "Once you know how easy it is, you think, why don't people just lie all the time? Why wouldn't they? It's so easy when you do it - and then you get everything you want."

Pretending to be American got Bain everything he wanted - at least for a while. Even so, if he could turn back the clock, he thinks he wouldn't do it again. The strain of it nearly destroyed him. But although it was his idea, he says it was not his fault. "We didn't create the reason why we had to lie. We didn't create that prejudice." In Bain's mind, the story isn't about the pair's duplicity - nor even what the hunger for fame will drive some people to do - but rather a tale of other people's prejudice.

It began back in 1999, 600 miles north, in Dundee. When Bain and Silibil - aka Billy Boyd - first met, everyone agrees it was "a match made in heaven". Both were studying graphics at Dundee College and burning with restless self-belief - the type of provincial teenagers who'd infer from an obscure taste in hip-hop their superior artistic destiny. "Me and Bill, we were both searching for something, and in each other we'd found someone we could be a team with and go and take on the world." Boyd was the good-looking, "super confident" one; Bain the "compulsive thinker", the strategist. "There was just so much to talk about, it was like explosions of fun all the time."

Together with another student, Oscar Kirkwood, they began writing and recording rap. Quickly convinced of their lyrical genius, in their minds fame and fortune were a formality. "We would sit around all the time and work out how we'd spend a million bucks. We'd live in such a dreamland, to the point where we knew exactly who we'd be friends with and just joke around and go, like [Bain puts on a cool, bored voice], 'Uh-huh, so what was Madonna saying to you last night, then?'"

They decided to reveal their talent at a showcase in London organised by Polydor. "Are you," it was billed, "the next Eminem?" The fact that neither Eminem nor any successful artist they could name had ever rapped in Scottish didn't strike them as a particular problem. The central preoccupation of rap, after all, was "keeping it real", and the Scottish vernacular was their real voice. "We wanted to show the world it doesn't matter where you're from, you can make it." Bain laughs. "We were 18."

Nothing prepared them for the humiliation they would suffer on that stage, and nothing has softened the memory of it for Bain. The three launched into their act, expecting the "intellectual, multi-metaphorical, multi-simile architecture" of their lyrics to blow the A&R men away. Instead, it reduced the front row to uncontrollable giggles. "Eventually we stopped," Bain recalls, "and they just laughed even more. They just laughed at us."

"Well, you're certainly entertaining - for a novelty act," one offered. "You sound," someone else suggested, "like the rapping Proclaimers."

"And that was it. We were heartbroken. We went back to Scotland with our tail between our legs."

It would take three more years for the ramifications of the insult to be fully realised, but Bain suspects its impact was probably decided on the bus home to Dundee. Kirkwood was indignant: "Fuck them, they don't know anything, what do they know, screw them, we did great, they'll learn one day", and so on. "But me and Bill, we had bigger ambitions, we knew we couldn't afford to think like that. Oscar was proud, Scottish proud. But I think me and Bill already knew in our heads what we needed to do."

To Bain and Boyd, the solution was self-evident. If they couldn't be Scottish rappers, they would have to be American.

Like most big decisions, it was easier to make than to commit to. Perfecting the accent was step one, but Bain had already grown up speaking in two different accents, for his family lived in South Africa until he was 10. At home in Durban he would sound just like his Scottish parents - then switch into South African with his friends. Adding another accent was relatively easy. Everyone agreed their demo CD sounded "a million times better" re-recorded in American. They submitted a track to a Radio 1 website and it received so many requests, Jo Whiley played it for a week. Not a single other thing had changed - not a beat, not a line - just the accent. To Bain, the equation was proven: American equalled successful.

Boyd still wasn't convinced. It was one thing to fake an accent for a song or a show, but could they fake an identity 24/7? Back and forth the pair argued, for almost three years. Was Boyd better at anticipating the long-term implications of the lie? "Well, I think he was scareder of what was going to happen in the long run. And me, I was just scared of nothing happening at all."

It sounds as if Bain came quite close to a nervous breakdown during their last year in Dundee. An insomniac since the age of 10, he had always been a worrier, periodically obsessive and over-intense. "I wasn't sleeping for five or six days straight, so when I went out everything was super bright. I was getting severe headaches and really living on the edge. We just had to get out. Every day was an incentive to suicide."

In the end it was student debt that settled it. Besieged by bailiffs, and behind in their studies, when they reached the point of considering robbing a Securicor van, they both realised they'd run out of options. With £350 between them, they quit college and took the bus to London, where they slept on Bain's big sister's floor.

He says there was still no concrete plan, even then. For the first few days they phoned up record companies still speaking in their own accents. "Hi!" they'd say. "We're a new hip-hop act from Scotland." And the line would go dead. So they started calling up as Americans. "'Yo, dude. We're over for a few days from California.' And just like that, we'd be invited to meetings."

He maintains that even when they stepped out on to the showcase stage in Soho a week later, they still hadn't made up their minds. Maybe they could perform in American, but still be Scottish in real life? "Then the guy from Island comes up to us backstage afterwards and the first thing he says is those words, 'Where are you guys from?' And that's it. We took a breath and, bam, out came a story. And from that moment on, we didn't stop acting."

Until that point, all they'd ever worried about was getting caught. "We never realised the real problem would start if we got away with it."

Every day for the next four and a half years, Bain pretended to be an American. He had sex in an American accent, swore like an American, got drunk in American. Eventually he had a Texan girlfriend, and even she never suspected a thing. By the time Bain stopped talking like an American, he and Boyd were no longer talking to each other. He had a major tax bill, a drink problem and a stomach ulcer.

When you pretend to be someone else, Bain agrees, you can't just take on a voice; you have to inhabit another ego. "I hated Americans - I'm totally anti-American. That's why we were so good at playing an asshole, because we hated that asshole." You also need a new biography - Bain and Boyd spent their first month in London making up their story.

They decided they would come from Hemet, a small city in California they'd heard of because Boyd's cousin lived there. Both aspiring young hip-hop artists, they first met at a rap battle contest in San Francisco - which they'd read about and could therefore describe in reasonable detail - and moved to Huntington Beach to work in skate stores, before a skate tour brought them to London. "We said we were trying to get a deal here, but if it didn't work out for us we'd go home."

The story trips easily off Bain's tongue - and after all, it is only a judicious adaptation of the truth. They did, due to "British heritage", both hold UK passports. They did hate the president. "We said we hate George Bush so much, we can't stand living in the country while he's in the White House." Even so, had anyone only asked them their home zip code, they would have been floored. Bain didn't even know how Hemet was spelt, or the difference between a town and a state. He'd never set foot in America. But as long as they acted loud enough and played crazy, it didn't seem to matter.

In just a couple more years they would have been too late, for the days when unsigned hopefuls got paid a lot of money were about to be over. But in 2003 it was still possible to live like pop stars without ever having released a record - or even signed with a label. After just six weeks in London, when they were down to their last £90, the pair signed a management and publishing deal with the manager famous for discovering Charlotte Church - Jonathan Shalit - for an initial advance of £70,000.

At Shalit's expense, they began work in a prestigious recording studio, the Dairy, and performing gigs. Island had assumed they would sign with them, but their management company had grander plans and touted the pair around London's major labels as the hot new act in town. They partied with record executives and swanned into London's celebrity circles with insolent charm. Picked for a football six-a-side tournament with Ray Winstone and Rod Stewart, they feigned ignorance - "Soccer, right? You pick the ball up and run?" - before playing everyone off the field. The louder and ruder they were, the more everyone seemed to love them; they were having the time of their lives.

When Kirkwood came down to visit, he could hardly believe his eyes. "We'd be in their house, chatting away normally in Scottish, then as soon as we'd get to the recording studio it was like putting on a different hat: now it's time to be American. And suddenly all these guys are going, 'Can we get you anything?' and running off to get them stuff. It was totally amazing how they had everyone wrapped around their fingers. It was mad."

A bidding war broke out between major labels eager to sign them, and in early 2004 they signed with Sony UK. Soon they were profiled on MTV's Spanking New, tipped alongside Bloc Party and Natasha Bedingfield as the latest new stars. Endemol held talks with them about making their own TV show, and MTV cast them in cameo roles in its stoner sitcom Top Buzzer. Clothing companies inundated the pair with free hip-hop fashion and endorsements, and they headlined the Nass Festival alongside the Sugarhill Gang. "People were just throwing money at us."

And the amazing thing was just how easy it was. "If you can convince one person, and then another person, eventually you have all these people believing in you, wanting something from you." As their social circle in London expanded, they would appropriate plot lines from TV shows and films, or stories they'd heard Americans tell, to flesh out their new identities. "We'd play around with different accents - we'd go, 'Fark off' and do loads of English accents, fooling around - and people were like, 'You should have your own TV show!' We did Billy Connolly and people were clean blown away by Americans doing such good Scottish accents."

But what had happened to their old identities? Back in Dundee, both had long-term girlfriends who weren't thrilled at being edited out. Bain's parents were supportive, but worried. "I was against it," his father says, "from the word go." But loyalty - and possibly the prize of vicarious fame and fortune - will persuade people to go to remarkable lengths. The girlfriends accepted that when they visited London they would be hidden away, and Bain's parents that their son would take their calls only if he was alone. Bain drew the line at talking in American to them - that seems to have been his moral threshold - but other than that he became adept at keeping his two lives apart. He did get a nasty shock one night, though. Out celebrating the birthday of Jamelia's manager, he glanced across the bar and saw, staring right at him, an old colleague from the skate shop in Dundee where he used to work. He spent the next half hour hiding in the toilets, sweating, until she had gone.

One challenge he and Boyd hadn't anticipated was their shortage of material to write authentic American rap lyrics. They had a song called Cunt, about hating Bush, with which they were happy. "But we didn't have any concept of the street, the ghetto, whatever. We're from Dundee, you know? We always wanted to write songs that were real - but essentially we're not real. We can't write gangsta rap songs 'cos we're not gangsters. All we'd ever been was students. So everything we'd write was about debt, or alcohol, or masturbation." Even this didn't seem a problem, though. When their label circulated the track Play With Myself to DJs for pre-release feedback, 48 out of 50 predicted it would be a top 10 hit.

Bain was discovering that he couldn't help pushing their luck. "Lying's like a drug. Eventually you get carried away, and that's where you're out of control. Telling the first little lie's a bit like smoking weed, but after a while you need a stronger hit."

One lie very nearly cost them everything. Bain and Boyd had just returned from a university tour when their manager phoned in high spirits with great news. "You know your old friends D12 [Eminem's hip-hop collective from Detroit]? Well, guess what, you'll be seeing them soon - you're supporting them on their UK tour!" Bain hung up, punched the air, and was turning to yell to Boyd when - "Wait a minute." His heart stopped. "Oh shit. Did he say 'your friends?'" And then it came back to him, his drunken random boast one night: "Sure we know Eminem. Yeah, and we're even better friends with Proof."

Proof and the rest of D12 were already on stage doing the sound check when Boyd and Bain arrived at Brixton Academy for their first tour date. With their manager looking on, excited to witness the happy reunion, there was nothing else for it; if lying is a drug, this must be the high. The pair took a deep breath, sauntered on to the stage, whooped, "Yo, Proof man!" and high-fived a man they'd never met in their life. "Been too long, bro! Cool to see you again!" And the hip-hop icon, taken unawares, high-fived and hugged the strangers back, and agreed it had indeed been too long.

When Bain is in the mood for moralising, he likes to point out that by the standards of the music industry, he and Boyd were no more fake than anyone else. "Everyone in the rap industry is acting, pretending to be something they're not. I mean, come on. Do they really go home and talk to their mum like that? You know what I've learnt?" he grins. "You can bullshit a bullshitter."

There was one unavoidable dilemma dogging them, though. They would become famous only when they released a record. And the day a record went on sale, they knew, "would be the day Scotland picks up the phone and says, hang on a minute, they're not from California. They're from Dundee. That's Gav and Billy - we used to go to school with them." The entire venture was pointless if it didn't produce a record - and doomed if it did.

The contracts they'd signed contained a clause that made them liable to repay everything, and possibly damages, too, if they were found to have concealed anything that reduced their commercial value. It's a standard industry clause that has kept many boy-band members in the closet - and by 2005 it was keeping Bain awake at night.

There had to be, he thought, some way round it. If they edged their music away from rap towards punk, then when people found out they were Scottish they might not mind so much - nationality-wise, rock was a much more accommodating genre than rap. And so they began recruiting new band members of a punk persuasion, mostly from the tiny circle of old friends and cousins in London who knew their secret. Bain called the inner clique "associates" - and for them, complicity in the lie was at first a lot of fun. Duping the industry was a laugh, and being in a band signed to Sony a dream come true. With limitless free beer, VIP passes and willing groupies, Bain and Boyd's flat became a non-stop party zone.

But it was a high-risk strategy. The reorientation came as a surprise to Sony and their management team, who thought they'd signed a pair of West Coast Eminems and wondered why they were mutating into a band full of South Africans and Scottish rockers. They had no intention of paying the new members - which meant Bain and Boyd were the only ones getting paid. In other words, they were expecting everyone else to lie for them every day - for nothing.

Slowly, resentment began to grow. The rest of the band became increasingly impatient to release the first record, reckoning sales their best chance of ever seeing any money, but here they came up against phase two of Bain's strategy. He thought he had identified a tiny window of opportunity in which they could out themselves as Scots and get away with it - just after they'd released their record, and before anyone else beat them to it. But it could work only if their record was so world-beatingly brilliant that fans would instantly love them too much to let anything change their minds.

What record could ever be that good? By the summer of 2005, they had recorded almost three albums' worth of songs but still not one Bain was ready to risk gambling on. Sony and their management team were running out of patience. They had spent well in excess of £200,000 on an act and still hadn't a thing to show for it. The band was disintegrating into feuds and factions, and Bain's drinking was completely out of hand. Terrified that one of his associates might desert and betray him, ill with paranoia, he was going to pieces.

His girlfriend in Dundee had finished with him the previous summer, fed up with the interminable deceit. Even Bain was tiring of the lies. Nothing he had achieved as Brains had ever quite belonged to him, and he was lying to almost everyone he knew. "You start to think, how could I have; I love these people, how can I lie to them like this?"

When the end came, it was still a terrible shock. Several associates and band members had already walked away, and Boyd's girlfriend in Dundee was pregnant. The couple had quietly married some months earlier, and to Silibil - if not Brains - it was clear that the adventure was over. Bain went out to Asda one night, and when he got back, Boyd and all his belongings were gone. He was on the bus back to Dundee. What was left of the band melted away within weeks. The management company stopped taking Bain's calls. The deal with Sony was dead.

"I was sitting at home on the sofa on a Friday night and I had the biggest panic attack. Two years earlier we'd been at a Christmas party in the Dairy recording studio, and the bass player from Muse was standing there, and the DJ put our song on, and he's like, you guys are going to be the biggest band in the world in two years. And now I'm watching TV, watching Muse headline the Reading festival, in front of 60,000 people, and I'm alone in a room. You know, it's hell when you're waking up in your flat and there are girls crawling off your couch naked, and you're like, who the hell are these people? But when you look around and you're alone, and you're not a rock star, you hit rock bottom.

"I jump on the bus, and I'm going up to Dundee, and this amazing thing happens. I meet this guy who works for Amnesty and he's telling me this story about a war, and I'm like, this is amazing. And he gets off the bus at Glasgow and I carry on to Dundee. And that's when I realise. The whole time, I spoke to him in American. And I'm sick to my stomach. I didn't need to lie to that guy. Why am I doing this?"

Plenty of people have written about why people lie and they draw strikingly consistent observations. Famous imposters and con men, from Raffles to Frank Abagnale, have all tended to share a common childhood theme: a successful father whose affluence is wiped out by disaster. For his first 10 years, Bain had lived the colonial dream - servants, swimming pool, sunshine. But his father's business folded and the shock of moving to a bleak Scottish tenement block full of junkies was shattering. Bullied at school and bewildered, he seems to have been trying to put something right ever since.

Studies also suggest that humans as a species are considerably more skilful at telling a lie than detecting one. Even highly trained professionals - customs officials, police detectives - are no better than the rest of us at spotting a liar. And the hardest lie to spot is one we want to be true.

Most of the people in the music industry I approach prefer not to talk about Silibil'n'Brains. An official spokesman for Sony says he cannot comment, as no one who worked directly with the act remains at the company, following its merger with BMG. Those I trace all stall for a while, then get back to me to say they've decided to say nothing.

Jonathan Shalit, the band's former manager, is the only one prepared to talk. He has a face-saving line to hand - "Everyone scams their CV, don't they?" - and insists their nationality made not the slightest difference to him. "The bottom line is, we signed them because we liked their music. Their [American] story was massively important to them - because they lived it. But from my point of view, the fact that it's turned out not to be true is irrelevant. If I'd signed them because of their story, I would have checked it out. But they could have been Brixton road sweepers for all I'd have cared. I would still have signed them, because their songs were good.

"You know," he adds, "the frustrating thing is that they could have been fantastic. They were fantastic. When they were together, they were really funny and had a lot of ideas, and TV companies were really interested in them for a while. That's the frustration; they were really good. I have very fond memories of them. But 99% of people in this business," he finishes briskly, "they're chasing rainbows."

The really distressing revelation for Bain and Boyd was that everyone they met, not just music industry types, was in thrall to the USA. For all the talk of a new anti-American mood in London, they found themselves treated far better in shops and bars than they had ever been as Scots, and more sexually attractive than they'd ever dreamed. "I went out with lots of girls who were a million miles out of my league. If I was me, Gavin from Dundee, they wouldn't even talk to me. But, hey, I'm Brains McLoud, who the fuck are you? Then it's a different scenario - you've scored them before you've even thought about it. People," he says indignantly, "are sooooo shallow."

The terrible thing was, he caught himself reacting in the same way. "Eventually, when we'd meet Scottish people or overhear them in a bar, we'd think, oh God, they're so uncivilised - we'd actually think things like that. We'd cringe and think, God, they are so unaware of the world."

Even though he no longer needed to, Bain continued to pretend to be American for two and a half more years. He formed a new punk rock band, the Unfortunates, then another, Hopeless Heroic, and tried to get signed again, unsuccessfully. He ended up in court over a massive Inland Revenue bill, having had too much fun being a pop star to think about paying tax. Jobless and broke, with a stress-related ulcer, he became a sales assistant in TK Maxx, and even had a go at becoming a male escort - before getting cold feet on his first job. And all this time, he still talked in an American accent.

He decided to end the pretence when it occurred to him to write a book about it. "For ages, all you're thinking is, how do you get out of this, how do you get it back? And all along you've been sitting on a great story and you hadn't even noticed." He still isn't sleeping much, for he is now feverishly writing in his lunch hours and through the night. He sees his memoir being made into a TV series or a movie, something between 8 Mile and Catch Me If You Can. Already he is calculating how to use the book to promote his band, Hopeless Heroic.

Bain never actually mistook himself for a Californian; his deceit was tactical, not delusional. But the self-belief demanded by modern ambition can teeter perilously close to self-delusion, and there is a heartbreakingly strange moment when he takes me back to Dundee to meet Boyd. The pair resumed contact only late last year and the atmosphere between them is cordial but uneasy. Boyd now lives with his wife and son, and has a skatewear shop; he shows a certain wariness towards his old partner in crime. How did he feel, I ask, when he walked away from their dream? "Relieved," he says bluntly.

There is a laptop on the counter by the till and Bain shows Boyd a clip on MySpace of Hopeless Heroic. Then they watch a video currently popular on YouTube - a spoof of an X Factor audition, where two British men rap badly in fake American accents and are taken to pieces by the judges. Stumbling out of the audition, heartbroken and dumbfounded, the rappers address the camera in a pastiche of the defiant post-audition interview. "We're not going to give up that easy. We know we've got the X Factor." Bain finds it hilarious and laughs out loud at the hapless pair, oblivious to the painful parallel.

Now almost 27, he remains optimistic that Hopeless Heroic will be signed, and that he has a big future ahead of him as a Scottish rock star.