The comic actor is starring in One Man Two Guvnors in the West End, but he fears people still associate him with the mis-steps he took after his hit with Gavin and Stacey. Will his new memoir redeem his public image?

In a small side room at the Guardian, with Al Pacino glowering from a poster above us, James Corden is performing a masterclass in modesty. He is quiet, contained, thoughtful. He rubs his nose, strokes his chin, considering his answers; if he had a forelock, I suspect he'd tug it. The main message is how fortunate he is. He feels privileged to be an actor, he says, grateful to appear on television, surprised at the breadth of his career, dumbfounded to be starring at the National Theatre. "I just feel lucky that I'm able to do so many different things," he says. "I feel constantly amazed that I'm allowed to, you know?" If he were a superhero, he would be Humility Man: leaping small molehills in a few stuttering, stumbling steps.

This is not the Corden I expected to meet. It certainly isn't the Corden that makes people shudder. Every time I tell someone I'm interviewing him they flinch visibly and a horrified noise explodes through their nose. The consensus seems to be that the actor, comedy writer, co-creator of hit sitcom Gavin and Stacey, presenter of sports gameshow A League of Their Own, is arrogant and loud, his humour laddish and dated, that he has an unappealing, thespy air of entitlement. Also, most essentially, he's attention-seeking.

The title of his new autobiography – May I Have Your Attention, Please? – confirms this last point. I had expected the book to be a mea culpa, an attempt to win people over, and it is in part. Corden emphasises that over the past 18 months or so he has changed enormously, since falling in love with charity worker Julia Carey and having baby son Max. But he certainly doesn't hide the side of him that sucks the air from the room. In the first few pages he writes about his earliest memory, aged four, standing on a chair at his younger sister's christening, pulling faces while people laughed. "This felt good. Really good," he writes. "In my head it became simple: if people are looking at me, and only me, it feels amazing. And that was that. From that day forward, every day became a quest to be noticed. To have the attention of people. Of you."

I searched for some explanation for this overweening neediness, riffling the pages with rising desperation. A dead parent? Dead sibling? Dead tortoise? Nothing. Admittedly, his father was once an RAF musician, who was sent to Iraq in the early 1990s as a stretcher-bearer, and while Corden says the day this was announced was one of the worst of his life – and the day his dad arrived back the very best – it's bizarrely flat in the telling. He writes about going to RAF Uxbridge for the homecoming, and launches into a grumpy aside about the catering. "Someone had tried to set up some kind of a 'buffet' in the mess, but they shouldn't have bothered. There were just lots of little bowls of crisps – rubbish crisps – and two bowls of peanuts. Now that's all right, but that's not a 'buffet'." This continues for some time. As I've scrawled in the margin: "seriously?"

I ask whether he was attention-seeking throughout school. There's a long pause. "Yeah, I was, and it's not something I feel particularly comfortable with, and that's why I chose that title for the book. Because when I look back I think, God, that's all it was ever about. And that was the case until not that long ago, is the truth, and I wonder quite what was missing or lacking … I have no idea what it could be, because [my background] couldn't be more stable. I wish I did have some sort of story where I was, you know, beaten as a child, but there was none of that. If you met my two sisters, they're incredibly outgoing, incredibly confident. They're brilliant performers. They could absolutely do this. But they just don't have that sort of hunger or desire, whereas for me it was burning inside."

Physically, he has long been on the large side, and when he was at school, he says, there were "two ways you can go. You can either hope and pray you don't get picked on, or you can, in a way, almost make yourself a bigger target, because it's harder to bully something that's really big. It's easy to bully something that's small and frail. And I think that a couple of years ago, when Gavin and Stacey went big, I think I probably – and I only realise this now, I didn't at the time – I think I probably did that then, too. I thought, if I make myself a bigger target then, I don't know …" he tails off. "I read some interviews now and I think, oh my God, you just sound so cocky, and I don't remember ever wanting that to be the case."

He was asked to write the book, reportedly for a seven-figure sum, and says his initial thought was: "I've got nothing to say … And then, and I don't know if this is true or not, but it was of great solace to be told that Kenneth Branagh wrote his at 26." (It was 28.) Corden is 33. "I thought, well, I have very much felt over the last year that a new chapter of my life is starting, and so, in that respect, it was quite nice. And at some moments painful too, looking back at a person who I don't feel is really me any more."

I can't help feeling he should have honoured his first instinct. The opening third of the book deals with his years growing up in High Wycombe, Buckinghamshire, with his social worker mother and his father, who is now a Christian book salesman. They were all in the Salvation Army, and it seems to have been a life almost comically, enviably free of incident. He writes about joining a school rugby team, attending after-school drama classes, forming amateur boy bands.

His stories suggest a slight slipperiness – hiding a school report from his parents, bunking off college, calling up a TV agony aunt and pretending to be a troubled schoolboy. Later comes the most revealing story of all, for me. He writes: "If nothing fun is happening, then I'll make something happen myself." So while working on Gavin and Stacey and staying in hotels, he'd call room service, "and when they showed up I'd sit in the corner and just burst into tears, really wailing like Will Ferrell from Anchorman. The poor hotel staff would be so embarrassed that they'd dump the tray and run away." He did this five or six times.

(My thoughts turn to this story at the end of the interview, when Corden's publicist arrives to take him to the next appointment. In the corridor we bump into a famous journalist from another newspaper whom Corden knows, and they fall into excited conversation. I was about to leave, but we haven't said goodbye. I try tapping him on the shoulder to just excuse myself quickly. Nothing. I talk to his publicist about her lovely shoes. It's all faintly awkward. I start wondering, idly, how Corden treats waiters. And I realise that, in his autobiography, he has given at least one eye-popping answer.)

Corden went to lots of auditions, but didn't have much luck until he was 17; after terrible GCSE results, he started a B-Tech in performing arts, ditched it, and landed a small role in the musical Martin Guerre, with three words: "Roast the meats." He'd always wanted to appear in the West End, he says. "And then, once I was actually in a musical and I was stood so far up the back, I thought: 'Hang on a minute! When I sat in the audience I never really thought about the 20 chorus people.'" He was offered another small role in Les Miserables, but instead began building a credible screen career, moving between serious films and populist TV: Shane Meadows's Twenty Four Seven, Channel 4's Hollyoaks, Mike Leigh's All or Nothing, ITV's Fat Friends. He landed the role of Timms in Alan Bennett's The History Boys, an enormous hit at the National theatre, then on Broadway, then in its film version.

He started writing Gavin and Stacey with his Fat Friends co-star, Ruth Jones, creating the role of loud, needy, beer-swilling Essex builder, Smithy, for himself. The show was a critical and commercial success for BBC3, and he was talked up as the golden boy of British comedy. The adulation included a double-page spread in The Mirror, with the line: "These gorgeous women can't keep their hands off cuddly comedian James Corden."

But a less likable side to his character was emerging. At the 2008 Baftas, for instance, he won best comedy performance for his role in Gavin and Stacey; the show also won the audience award for television programme of the year. Arriving onstage to collect this second award he ungraciously asked why the show hadn't been nominated in the comedy category too. As he says in the book, he was met "with silence, shock and disbelief" from the audience. It wasn't the only embarrassing incident. "I would go to awards ceremonies," he says, "and make a point of making jokes, digs. I was lost." On one occasion he had a violently embarrassing spat with Patrick Stewart, admittedly provoked by Stewart. On another, he called TV critic Gareth McLean "a fucking twat" from the stage. "Which is so irresponsible. So stupid. So naive. It really paints a picture of someone who's not aware of the world they're living in. Because all Gareth McLean ever did wrong was to not like our TV show. That was it. And he is absolutely well within his rights to do so! What kind of altered state must you be in to go and do that?" Was he drunk? "I don't even think so. I was just so lost." He has since apologised personally. "And I meant it."

In 2008, he was being rude to his agent, and to Ruth Jones too. "I wasn't doing myself justice, in any part of my life," he says. His co-star in Gavin and Stacey, Rob Brydon, took him aside and told him he was in danger of being an idiot. He had been in a long-term relationship from his late teens, which had faltered when he took The History Boys to Broadway, then ended. He hadn't felt comfortable in Buckinghamshire since. "I'd never really lived in London before," he says, "and going back to Buckinghamshire made me sad because it was our home, me and my first girlfriend." So he kept his clothes in his car, and would often crash at the house of Dominic Cooper, his co-star in The History Boys.

He was going out all the time, which was "intoxicating", he says. "I'd never been single, I never went to university, I'd never gone out drinking – that thing of, Oh my God, we're getting in a cab to a party, and then you end up with some girl. I'd never done a single minute of that, and that alone can be a destructive force. Coupled with being a little bit famous, it's like …" He makes the sound of an explosion, throws his hands in the air.

If there was ever any doubt that he adores the company of celebrities, it is dispelled by the book, in which Piers Morgan is "an incredibly nice guy", Michael McIntyre's talent blows him away and Andy Murray is "one of the warmest and funniest people I've had the pleasure to meet". It includes a scene that tells you all you need to know about the boys' club of British comedy. Corden, Steve Coogan and David Walliams visit a lapdancing club in Greece in 2002. "About 30 seconds into the dance," writes Corden, "just as the girl in front of me was lowering her ample breasts into my face, I looked over at Steve on my right and he looked back at me and shouted 'AHA!'"

In February and March 2009, he had three big projects due to air, all with Gavin and Stacey co-star Mat Horne. There was their BBC3 sketch show, Horne and Corden, the hosting of the Brit awards, and starring roles in the film Lesbian Vampire Killers. All three were critical failures. When Corden talks about them now, he veers between regret and a bullishness that sees his air of modesty slip. He says he got seduced into making Lesbian Vampire Killers "by thinking, 'Oh my God, I'm being offered the lead in a film.' The lead in a film! I never thought I'd be doing that." When it comes to the sketch show: "I just think we didn't do it right, is the truth. We didn't take our time with it."

But then he says: "You can't make anything without making mistakes, do you know what I mean? Robert De Niro's in the Rocky and Bullwinkle film. There's a lot of far greater people than me who have made mistakes in their careers … There's loads of people who have made stuff that isn't good, and never get asked about it. No one ever goes, 'Oh, I'd like to just spend a long time talking about your failure a couple of years ago.'"

The fact is, Corden is a genuinely talented actor. A week or so after we speak, I go to see One Man, Two Guv'nors at the National, a comedy in which he takes the lead as a young man working for two highly demanding bosses. It's Brighton, the early 1960s, a world of farcical seaside humour, and the play is a joy, as reflected in its five-star reviews. Corden is physical (smashing himself in the head with a dustbin lid) and funny (a scene where he has to serve dinner to both bosses has people howling). A posh, older couple behind me look up his name in the interval. "James Corden," they say. "Never heard of him. Awfully good, isn't he?"

The show is about to move to the West End; if Corden was content just to pursue acting, I think he'd win back any detractors. But as he says in the book, these days, "I'm not sure people even think of me as an actor at all." Instead, they see him as a comedian, a celebrity. And his yearning for attention means he'll probably always spread himself thin. He says he loves hosting TV shows, he's currently writing a new comedy for BBC2, and of course there's the autobiography. I'm intrigued by its structure. In the opening pages his son has just been born, by page 132 he's two days old, and at the end Corden is picking up his partner and baby from the hospital. Had he written it between his son being born and coming home from the hospital? He butts in: "Yes, I absolutely had." I don't know quite whether to believe him. So it was written in a week? "Sure." He winks. The trouble is, it shows.One Man, Two Guvnors is at the Adelphi Theatre from 8 November, currently booking until 25 February 2012