Daniel Radcliffe has one of the most recognised faces in the world thanks to a certain boy wizard named Harry Potter.
In fact, after seven years playing JK Rowling's creation there can't be many places where the 19-year-old isn't known. "If I find that place, I may move there!" he jokes.
Dressed simply in a red shirt and jeans, Daniel's clutching a can of Diet Coke and scanning the hotel suite in London with curiosity.
Either the caffeine's taking effect, or he's just naturally full of beans, because once he starts talking about something, the words just flow in an (almost unstoppable) torrent of excitement.
He's just finished filming the latest instalment of Harry Potter and, despite his bouncy demeanour, insists he's exhausted.
"If I wasn't here, I'd be in bed probably now. I know it's coming up to two o'clock in the afternoon, but that wouldn't matter to me!
"I've never felt this tired before, normally I have a lot of energy. I still do have a lot of energy, as you can probably tell, but for some reason, just before the end of a film, your body starts to let itself wind down.
"Diet Coke is a big help, although I did hear something rather disturbing about it recently," he adds, heading off on a tangent.
"No, it was about full fat Coke - apparently highway patrolmen in certain states of America carry two litre bottles of Coke around with them to wash blood off the roads... but hell, it tastes good, so never mind!"
It's this clear thirst for and love of knowledge that makes it so hard to distinguish Daniel, in the flesh, from his on-screen alter ego.
He admits that curiosity is a quality he's picked up from the wizard student.
"What's great about Harry is he doesn't take no for an answer, he doesn't accept what people are saying, he always questions things and tries to go beyond what people are telling him and in the end that is both the downfall and the salvation of his character," he says.
"I think curiosity is a lovely quality to have and just a lust for knowledge's sake. Also, what I think all kids have learnt from him is just the value of friendship and how important friends can be to life."
Harry Potter And The Half-Blood Prince, the sixth film in the highly successful franchise, once again pits Harry and his faithful sidekicks Ron Weasley (Rupert Grint) and Hermione Granger (Emma Watson) against dark forces.
With the evil Voldemort on the rise, the students at Hogwarts have to be ever more vigilant about who is among them.
Returning teacher Professor Horace Slughorn (Jim Broadbent) provides Harry with valuable knowledge about his former pupil Tom Riddle, a boy who would grow up to become a threat to the wizarding world.
There's also romance in the air, as Ron gets a new girlfriend, making Hermione jealous, and Harry kisses Ron's sister Ginny (Bonnie Wright) for the first time.
"It was weird, because I've known Bonnie since she was nine. I was 11 when she was nine, I hasten to add. It was weird, because when Katie Leung was brought in to play Cho (Harry's first love), we all knew she was going to be the love interest, but with Bonnie as Ginny, she was just brought in to play Ron's little sister, so it was kind of odd kissing her."
That said, Daniel claims he wasn't nervous about the scene. Partly because he had just been performing in a West End and Broadway production of radical Seventies play Equus, which involved getting his clothes off every night.
"I'd been naked on stage by that point, so there's not much else to worry you," he jokes. "But I later found out that Bonnie was nervous, so I could have been a little bit more sensitive about the whole thing.
"There's things on film sets which no one tells you, like for Christ's sake don't stick your tongue in! Luckily, I have never made that mistake, but no one tells you and you're too embarrassed to ask. Generally speaking, unless your co-star does, Don't! It didn't stop me from trying though..."
He's tight-lipped about his current off-screen romance, with Equus co-star Laura O'Toole, but seconds later is happily chatting away about his celebrity crush on Sophie Dahl.
"She was at the fifth film premiere and kissed me on the cheek. I turned round to her and said, 'Thank you, because you've given me closure on my adolescent years'. I also got a note from her congratulating me on how I'd presented an award at the Baftas and I think we know that means she wants to marry me!"
What would Jamie Cullum say? "He'd accept it, he'd have to live with that!"
For all the fame and money - he reportedly signed a contract worth more than £25m for the final Harry Potter films - Daniel's a normal, if fairly intellectual, teenager.
During breaks from filming, he and Rupert play table tennis, or watch daytime TV and old war movies. He writes poetry in his spare time and stays in touch via letters.
"It's a very very old-fashioned thing to do, but I love it, because I know nowadays it's a very special thing when someone gets a letter."
He actually thinks his fame is "hilarious", explaining: "I find it bizarre, because I meet people who I admire and respect and who I'm a fan of. I'm really nervous about meeting them, and then I think to myself, 'God, this is how people feel when they meet me', and that's a peculiar feeling."
He has hordes of screaming female fans all over the world, but insists they only fancy the red carpet version of himself.
"The me who sits in a darkened room for eight hours watching cricket and eating a big bowl of pasta in my socks and my underwear is not nearly as appealing to women!"
He continues: "It's not the fame part of things I enjoy so much, because that barely ever comes into my life. I enjoy the filming."
Daniel and his co-stars are currently a few months into a gruelling 19-month shoot for the seventh and eighth films. The final book in the series, Harry Potter And The Deathly Hallows, has been split into two.
While the cast lists still read like a Who's Who of British acting talent, for the final instalment there's no Michael Gambon, who plays Hogwarts head Albus Dumbledore.
Daniel admits it was emotional filming the final scene with Michael. "It was very disheartening, because I love working with Michael, I love him as a man as well, so I'm a bit annoyed I won't get to see so much of him.
"Just as I was really sad when Sirius died because I love working with Gary (Oldman) and he's a little bit of a mentor for me and he always has been."
Considering the acting education he's been given by working with stars such as Dame Maggie Smith, Ralph Fiennes and Alan Rickman - who reportedly cut a holiday short to help Daniel with his role in Equus on Broadway - it's no surprise to hear the young actor has decided against continuing his studies at university, and will go into acting full-time.
In his first post-Potter role, he's set to play photographer Dan Eldon, who was killed in Somalia, aged 22, in The Journey Is The Destination - funding permitting.
"It is a long way off at the moment, but it's potentially a very exciting thing for me.
"The greatest quality I think people can have as actors is their fearlessness and their willingness to try something even if they think they might fail, to try it anyway it's that kind of fearlessness that I aspire to certainly."
But does Daniel have any desire to play a bad guy for once? "I'm not sure how many baddies are five foot five, but still I'd like to play one very much indeed. If you meet any producers, tell them I have a wonderful evil stare!"
Extra time - Daniel Radcliffe
:: London-born Daniel is the son of casting agent Marcia Gresham and literary agent Alan Radcliffe.
:: His first acting role was as a young David Copperfield in a BBC adaptation of the Charles Dickens novel in 1999.
:: In 2007, he played Rudyard Kipling's son, who died in the First World War, in the ITV drama My Boy Jack.
:: Daniel suffers from a mild form of dyspraxia, which affects his hand-eye co-ordination, so he can't swim or ride a bike.
:: In the first Harry Potter film, he played a practical joke on co-star Robbie Coltrane, which earnt him a reputation as a joker, but he insists he's never done anything like it since.
:: In the world outside of Hogwarts, Daniel and Tom Felton, who plays Malfoy, are good friends. They even go to the cricket together.