Booze, nudity, excess: At 23 Harry Potter actor Daniel Radcliffe looks back on a (partly) misspent youth - and acting with Mad Men's Jon Hamm

He had his first kiss on a film set, got naked on stage at 17, and gave up drinking at 20. So what kind of adult has he become? The answer: a very polite one

'I've got to start," says Daniel Radcliffe, "by saying my mum sent me a column you wrote." For a moment, I'm thrown. I've got half an hour to interview one of the most famous young men in the world, which is less time than I've ever been given to interview anyone, and he's talking about my work? The column, it turns out, was about Israel and Palestine, and mentioned a TV series called The Promise, which his mother cast. The column, from what he's saying, was a masterpiece. And Daniel Radcliffe is clearly a very astute young man.

I've already been impressed by his manners. He's polite to the photographer, polite to the PR, polite to the various people milling around the hotel suite who are all there, it's clear, because of him. He's polite as the photographer snaps, and asks him to look this way, and that way, and out of the window, and polite as the photographer leaves. And now that we're on our own, on a sofa, in a Soho hotel room, he's being very, very polite to me.

He's being so nice that I want to be nice back. I want to tell him how much I love his work, but actually, it's a bit tricky. I didn't see him in Equus, which he starred in five years ago in London, and four years ago on Broadway, and which got him proper rave reviews. I didn't see him in How to Succeed in Business Without Really Trying, the Broadway musical he did last year. I did see The Woman in Black, James Watkins' film of Susan Hill's novel, which came out in January, and was the highest-grossing British horror film for 20 years. But I can't really say that I thought the novel was brilliant, but the film was a bit ridiculous, and that although he was very good at looking frightened, he did have to do it an awful lot.

And I can't say all that much about Harry Potter. I don't, for example, feel that I can tell him that I haven't read a single one of the books. I can't really say that I don't have children, and I don't see why a grown up would read children's books if they didn't have children, and that I only had three days' notice for the interview, which wasn't enough to catch up with eight films and seven books. I could, I suppose, tell him that I did go to the video shop and get Harry Potter and the Deathly Hallows Part 2, and that as far as I could tell he was very good in it, but I don't really feel I could tell him that, even with a Wikipedia summary in front of me, I couldn't work out what was going on.

And I can't tell him that he's brilliant in A Young Doctor's Notebook, the new series he's starring in, with Jon Hamm, for Sky Arts, because I've only seen a tiny clip. But I have read the book. It's based on a Mikhail Bulgakov book. And I do know, because I have, at least, managed to do a bit of reading, that Daniel Radcliffe is a very big fan of Bulgakov. I know, in fact, that The Master and Margarita is his favourite book. And so, because I want to be nice, just as he's being nice, I ask him about his favourite book.

"I read it," says Radcliffe, and his clear, blue eyes look even bluer as he says it, "and immediately loved it, and read it again immediately afterwards, and then, for my 21st birthday I went to Russia to visit his apartment, as my present to myself." I'm smiling. I can feel I'm smiling. I'm smiling not just because I want to be nice, but because one of the richest young men in Britain, who's "worth" £40million, and who has houses in New York and London and Australia, and artworks by Damien Hirst, and who can buy pretty much anything he likes, thinks that the best present he can get himself is a visit to the home of the dead author of a Russian book.

"The first time," says Radcliffe, "I went there alone. And then, when I did The Woman in Black press, they took me around, and I kind of seemed more knowledgeable about it than the interviewer. But my friends have always called me Mr Thorough, in that when I get into something I become obsessed with it." From the way he's talking, you can see he might. From the way he's talking, you can see he might do quite a lot of things with the kind of energy that has other people running to catch up. After reading the book, he saw The White Guard at the National Theatre, and then read A Country Doctor's Notebook. Two years later, he was approached to play the young doctor in the TV adaptation. "They had no idea," he says, "that I was this obsessive fan."

A Country Doctor's Notebook, like The Master and Margarita, is very, very funny, and very, very dark. It's based on Bulgakov's own experiences as a young doctor on the eve of the Russian Revolution. The horror in it – the horrible diseases, the weird growths, the bloody amputations – is described in such deadpan tones that at times it seems surreal. But it isn't. The Master and Margarita, on the other hand, which tells the tale of the Devil's visit to Moscow, is. It's a kind of magic realism. It is, you might almost say, magic for grown ups. It is, you might almost say, magic for a child wizard who has grown up. Couldn't you?

"Yes, absolutely," says Radcliffe. "But I think that's in me anyway. I've always had a slightly overactive imagination. Bulgakov clearly did as well. I find the book fascinating," he adds, "because of the way it was written." It was written, this son of a literary agent reminds me, over about 14 years, in secret, and only published 30 years later, in censored extracts in a magazine. Within days, he says, "people could quote passages to each other on the streets". Within months, some of the phrases in it, like "manuscripts don't burn", had become part of the Russian language. Within months, in other words, it had a mass impact on a whole culture. Like, for example, Harry Potter?

"It is," says Radcliffe, and he doesn't seem to flinch at the question, "something that has. It's in the collective consciousness of a generation, and there are words that are now filtering into the language, like Quidditch and Muggle. It's a shared set of references, I suppose, and it's quite universal. Potter was so massively wide-ranging, and read by everyone." I nod. I feel a bit guilty, but I still nod. It was read by pretty much everyone. Just not, unfortunately, by me. "I'm always pleased," says Radcliffe, and he sounds as though he means it, "to be associated with something that was so important. And it's not just a franchise. It's only really in the past few years that that word has been bandied around, and it makes everything seem very cold and business-like. We were always wanting to prove ourselves and get better with every film."

Well, yes. It's already clear to me that Daniel Radcliffe is the kind of person who's always trying to do things better. This, after all, is a man who learnt to sing and dance from scratch for a Broadway musical. This is also a man who had never acted in a theatre and who, at 17, took on a starring role. And not just any starring role, but one that meant he had to face the world, or at least a West End audience, stark naked. The young doctor in A Young Doctor, I remind him, is almost paralysed with fear at the terrible tasks – the hacking, the digging, the chopping - he has to take on. It looks, at least from the outside, as if fear is quite a motivating factor for him, too. Is it?

"Oh, it's very motivating," says Radcliffe, with an eagerness that has me smiling again. "I don't want anyone ever to say 'you know, maybe somebody could do Dan's job better than him'. In the past, they could legitimately say that at certain points. I haven't always been thrilled with my work. But the fear of not proving the people wrong who think you can't emerge from a franchise and do well, that's a very strong driving force."

It sounds, I say, as if he swings between massive confidence and massive insecurity. Radcliffe laughs. "With any kind of artistic thing," he says, "it's a muscle, like any athlete, and the moment you're not doing it, you lose all confidence. That's why I'm terrible with down time. And actually," he says, "what's been great about the last year and a half is that I have found a confidence. Before, basically, by the time we got to the end of Potter, I was going 'I don't know if I can do this, I don't know if I'm good enough'." He tells me about Gary Oldman, who turned to him on his last day of playing Sirius and asked if he thought he'd been any good. He mentions Tom Brady, the American footballer, who says, apparently, that he wants "to earn it" every single day. "I think," he says, "the things I have on my side are whatever ability you have naturally, but on its own that's worthless, you have to want to work."

Ah, yes, work. Well, Daniel Radcliffe clearly does want to work. Between the afternoon and evening shows of How to Succeed in Business Without Trying, he would, he says, watch boxing he'd stream from Sky. "I'd go 'you know what, if they can do that, I can do that again', because even though my body was falling apart, I was, like, they're doing that and getting punched." Before he did Equus, he worked with a voice coach for 18 months. "Not," he says, "that I was by any means the finished article by the time I went on stage, but I was a lot further along than I would have been if I hadn't done that work." You might, in other words, be able to succeed in business without trying, but you sure as hell can't in theatre, or film.

He has, he tells me, just finished filming Kill Your Darlings, about a period in the life of the Beat poets. It is, he says, about "young love", but it's "also a story of a liberation". It will, he thinks, be "more irreverent" than Walter Salles' On the Road, which, at the time we meet, isn't yet out. Radcliffe plays Allen Ginsberg. Many bookish young men, I tell him unnecessarily, find the whole Beat thing incredibly glamorous. Does he?

For a moment, he looks torn. He wants to be polite, and give me the answer he thinks I want, but he doesn't want to lie. "Not as much," he says, in the end. "I used to write a lot of poetry, I would always use form and metre and rhyme. I love all that stuff." He wrote his poetry, for fairly obvious reasons, under a pseudonym. He sent it off to Stephen Fry, and Tony Harrison, and got "great responses" from both. If Harrison said he liked it, I tell him, I think he probably did. At a poetry reading I once organised, he certainly wasn't slow to criticise the wine.

The Beats' work was, of course, all about youthful excess. A Young Doctor's Notebook, on the other hand, is all about feeling too young to be doing what you're doing. Radcliffe has, in a way, been too young to be doing what he was doing since he was about 10. He grew up on a film set. He had his lessons on a film set. He had his first kiss, and his first relationship, on a film set. He has spoken, I remind him, about feeling more comfortable in the company of adults, and feeling like a fish out of water at school. Is it a relief to have stopped being a child, and to be allowed to be a young man?

Radcliffe smiles his sweet, polite smile. "I said to my mum, when I was seven or eight, I was in the bath, 'I'm not good at anything, I'm not good at sports, I'm not good at school, and I remember my mum saying 'but you've got social skills', and I remember turning round to her and saying 'that doesn't count'. When I say I wasn't good at school, I do mean that." I fight an urge to hug him. He's so clever, and eager, and polite, and nice, and he wants to tell me how bad he was at school.

He didn't, he explains, do well in class, because he couldn't shut up. "I've always," he says, "loved talking to people. I've always been very curious about everything. I think it's the most important quality anyone can have." So do I, but he still hasn't exactly answered the question. "I am getting an impression," he says, when I remind him what it was, "that I'm starting to be seen as a young man, which is lovely. I thought that would take longer, to be honest, but it hasn't."

At 23, he seems to have put his own youthful excesses behind him, which could make some of us feel quite old. He has, for example, stopped drinking. There was a time, which started when he was 18, when he would drink until he blacked out. He drank on his own and became "a recluse". At 20, he gave it up, and is now teetotal. Does it feel a bit weird to be already looking back on a (partly) misspent youth?

For a moment, Radcliffe's smile fades. This, it's clear, isn't his favourite subject. "There are," he says, "other ways of having youthful excesses! I don't want to give the impression I'm a boring bastard that never goes out. I still have a really good time. It's about going 'if I continue like this, I will jeopardise my career, and the thing I love'. I've been working every day since I was 11. I don't know how to not work, it's what I love doing. In fact my identity is so wrapped up in who I am when I'm on set that I kind of need to work on that."

The drinking, of course, was about the pressures of celebrity. It must, I tell him, be awful to feel that the only privacy you ever get is in your own home. It is awful. It's clearly awful. But Radcliffe won't say so, even though he's said so before. "There is," he says carefully, "an upside to fame, in that hopefully next year a shitload of people are going to be introduced to Allen Ginsburg. A lot of people would not have gone to see Equus, and have been introduced to that play. They can come in for the wrong reasons, I don't care. As long as they stay for the right reasons, because the material is good."

The main thing that annoys him about celebrity, he says, is that people assume he thinks his opinions have a higher value because he's famous. "I'd just like to take this opportunity," he says, "to make it clear that I don't. I just answer these questions because people ask."

Sadly, our time is up. I feel I could talk to him all day, but our time is up. But two and a half months later, on a flying trip to London, and in the same hotel in Soho, he agrees to see me again. He has just finished filming a film called The F-Word. He's just about to start filming a film called Horns. His holiday, if you can call a weekend spent partly talking to journalists a holiday, is two days. "You can't," he says, "wait around. It's so hard to get any film made. When the opportunities are there, you have to take them." But surely, I say, this must take its toll on his private life? And is he still with his girlfriend, Rosie? "I'd love it," he says, so politely I feel like the worse kind of hack, "if we didn't talk about that."

So we talk about the new films. We talk about fame. We talk, because you can't not when you're with Daniel Radcliffe, about the importance of work, and how laziness pisses him off. I mention manners. He has, I tell him, got really lovely manners. "I just don't," he says, as if this was completely normal for a film star, "really have it in me to be rude."

And then we go downstairs to a screening room to watch the first two episodes of A Young Doctor's Notebook. It's very funny, in a much more slapstick way than the Bulgakov short stories, and very dark. It's very well scripted, and very well acted, with a very handsome, very tall Jon Hamm as an older version of the doctor, and a very handsome, rather short Daniel Radcliffe as his young self. And Daniel Radcliffe is great. He has top notch comic timing, and he's great. Daniel Radcliffe is, in fact, not just very nice, and very polite, and very hard-working, and very bright. He is also, I can finally tell him, and do, over a glass of wine for me, and a glass of water for him, at the drinks after the screening, a very good actor indeed.

A Young Doctor's Notebook starts on Sky Arts on 6 December at 9pm.

This article appears in 1 December print edition of The Independent's Radar magazine