The interview begins in the standard way: "Can you remember the first time you picked up a racquet?" I ask.

"No, I don't remember that very moment. I think it was a wooden racquet because I have pictures of it," he replies, and almost instantly he is all things Federeresque: charming, warm, self-effacing as he relays lending the racquet to a friend and never getting it back.

"At the beginning I used to go out and play with my parents [who'd] spend the weekends at the tennis courts, socially." During the week, he'd be "hitting a ball against the wall a lot, and against the cupboards, and against the door of my grandparents' house." He smiles. "I think boys in particular get very excited about throwing and catching balls - and breaking things."

At 13, Federer entered Switzerland's National Tennis Training Centre, only returning home on weekends if he wasn't playing an event. "I used to cry a lot on Sundays at 6pm when I took the train [back], so I was very homesick, but I think it made me tougher. It was good for me to grow up a little bit by myself. I think I got the right coaching at the right time. I realised quickly that I was talented but definitely not great yet, so I had to put in the hard hours. Then at 16 I stopped school, and said, 'I'll give it a go on the professional tour.' And I sort of never looked back, because I rose in the ranks very quickly."

"Did you like studying?" I ask this because his game can appear so mathematical: he finds angles no one else can see, using the court like a chess board.

"Not so much," he says. "I had a hard time. I just felt like it took me longer than some other kids at school who just read one book, they know everything about it and they remember everything. My mind was always, 'I want to go outside, go play tennis.' "

But Federer concedes, "My anticipation and awareness of geometry on the court has always been very good, and especially now in the modern times of the game, that we can hit with so much top spin and so much angle, you need to utilise these corners."

But how did he go from being a talented junior to having a game, as the late author David Foster Wallace put it, full of "beauty and genius ... mystery and metaphysics"?

"I don't exactly know why it all came together that well," Federer says, as though still grappling with the phenomenon himself. "But I was always the kind of guy who needed to understand: why am I going to the weights room? Why am I spending four hours on the tennis court? Why am I playing these tournaments? And once it all made sense, it was like a very interesting grid in my mind. It all matched up, and that's when I was able to play my absolute very best."

Federer's "best" has led him to 17 grand-slam victories to date. Many regard the 32-year-old as the greatest tennis player of all time. He reminisces about his early days on the circuit, how even in the beginning he found "meeting different people, and different cities and cultures ... a joy. It's chasing a dream." I ask what it's like to live that dream.

"It's a great feeling. I try sometimes to look at it when I'm getting too down on myself and getting too negative. I say, 'Why am I getting so worked up about this?' But that's because I have the instinct, hopefully, of a champion. I want to win. I don't want to lose. When it's not happening, it's super frustrating. But all the records I have achieved, I have that in the bag, and it does give you a relaxed mood more often than not."

"You only have five minutes," says the publicist, suddenly breaking any spell. "So if you can include the Moët questions?"

Federer is a global ambassador for Moët et Chandon - it is reported that he's being paid $US30 million ($33.2 million) over five years. The publicist has twice emailed me, stipulating that Federer's involvement with Moët must be discussed, although I've given non-committal replies.

"So do you drink a lot of champagne?" I ask. He looks only slightly uneasy as he answers, "Selectively, in certain moments. I like to celebrate more today. When I was younger I was running from one thing to the next. There was so many things going on in my mind that my first success, you want more of it, you become a little bit addicted, but today I try to savour moments more. So it's not only on the tennis court, it's also when I catch up with friends. There's always something to celebrate and then I try to open a bottle of Moët et Chandon." Surprised at how blatant this is, I try to steer us toward his charity. The Roger Federer Foundation has been running for 10 years and supports educational projects in a number of poor communities, including in South Africa, where Federer's mother grew up. The night before our interview he'd played an exhibition match against France's Jo-Wilfried Tsonga, raising more than $1 million for new projects. "It's something close to my heart," Federer says. "We've been able to touch the lives of 86,000 kids, and we're trying to aim by 2018 to reach a million kids."

"Is it a shock to go into the impoverished communities in which you're working?" I ask.

"Not so much," Federer replies. "I actually get very inspired and motivated seeing it. People think that [the children] are all very sad just because they're poor. It's not the case. I didn't see one crying kid when I was there, so they have their good times. They only know this life and it's a very hard life, especially when you don't have enough food or you don't have the education, so when I go there I really come out so motivated that I want to do more."

When I mention that he appears fitter than ever, Federer hears this as "The Retirement Question". "For me it's very much about the love of the game," he answers quickly. "Because that's what I wanted to do as a little boy and, for me, it doesn't go, 'Oops, it's gone'. As long as the body's holding up and the mind is fresh, I don't see a reason to stop. A dream of my wife is that our family [he and wife Mirka have four-year-old twin girls] can see me play. Like in Brisbane, I'd look up and see them either reading a book because they're bored, or giving me a wave."[Federer and Mirka are expecting their third child this year.]

"You have one minute: if we can maybe have one more reference to Moët et Chandon," says the publicist. "Maybe you can talk about the 2004 vintage and why that's so important and special to you?"

"In 2004, I became world No. 1," he says. "It's the one I try to open whenever it's a really big occasion for me, so that's my favourite." Federer's voice trails off. He's self-conscious.

"I guess these endorsements must help your foundation?" I ask.

"I don't put any pressure on any of these sponsors to tell them they have to be part of my foundation," he says. "But if they do decide to support it, I'm the happiest man in the world." The publicist calls time on the interview while Federer makes an apologetic face. As I leave the hotel suite, he is already sitting in an adjoining room talking to a journalist from Vogue.

A full row of magnums is stacked behind him.

I'm later ushered to a crown terrace, where a cocktail party is under way in honour of the man himself. People stand around in "glamour tennis whites" holding gold goblets stamped with a four-letter champagne brand, beginning in M and ending in T, and I realise I've blown the interview. I thought it was about a game. In fact it's a story about the commercialisation of modern sport. While his playing career has been in decline, Federer is still believed to make more than $US40 million annually from sponsorship deals with brands including Nike, Rolex, Lindt, Gillette and Mercedes-Benz. (To put this fortune in perspective, his total career prize money is a record $US80 million.) So do young players coming up now dream of winning trophies or brand power?

Phil Johnson, a marketing specialist who also writes for Forbes, explains the advertising appeal of elite athletes taps into our "desire to witness the ultimate experience of what a human being can achieve [and] if we can't accomplish these things ourselves, we want to get as close as possible to one who can". Preferably one not discovered running a sophisticated doping syndicate, or crashing his SUV into a tree before being found shagging everyone within a 30-kilometre radius. Preferably a Roger Federer.

Federer arrives at the party and with good-natured ease tells the guests that tennis is a very elegant game, like Moët, and it's a dream come true to be a global ambassador for the brand.

He sits on an umpire's chair to officiate a game of "tiny tennis" that's taking place on a miniature court between the party-goers, while keeping up a stream of funny, natural banter. The thing is, he's almost as brilliant at this as he is at playing. Plus, the man is squeaky clean without being a nerd, debonair while remaining thoroughly masculine, and in possession of godlike talents while seeming to be down to earth. And because he's deep in the business of selling corporate inspiration, even if we never again witness the pure magic of his game we're destined to be reminded of it on placards and internet pop-ups for many years to come.