How did Roger Federer become the greatest? He was not born in Sweden (Bjorn Borg). He was not shaped by a dominant parent (Ivan Lendl). He is not fuelled by rage (Jimmy Connors) or tortured by demons (John McEnroe). He has never had sex in Nobu (Boris Becker), smoked crystal meth (Andre Agassi) or been afflicted with odd sleeping habits (Pete Sampras). He is as affable as Tim Henman.

Somebody will have to explain him.

We meet in Basel, the city of his birth. He is looking fit and relaxed after a lengthy break from the most remarkable season of his life. It began in tears at the Australian Open in February, when, six months after losing the greatest final ever seen at Wimbledon, he lost again to Rafael Nadal.

It was his fifth successive defeat to Nadal in a final, and it raised an interesting question: how could he be deemed the best of all time when he might not be the best of his own era? But the obituaries were premature.

In April, he married his long-time girlfriend, Mirka Vavrinec, and a month later beat Nadal to win his first tournament of the year at Madrid. In June, he won his first French Open and equalled Sampras’s record of 14 Grand Slam titles. In July, he beat Andy Roddick in an epic final at Wimbledon to surpass the record, and became a father two weeks later when Mirka gave birth to twins. In September, he lost the US Open to Juan Martin Del Potro — his sixth consecutive appearance in the final.

He did not marry a supermodel (Roddick). He does not make fun of his rivals (Novak Djokovic) or pick continually at the crack in his backside (Nadal). He has worse fashion sense than Andy Murray.

How does he explain it?

He begins with a story about a script he received for a commercial for Nike with Tiger Woods in 2007. “We had these different lines,” he explains,” and I was reading through it and said I’d like to take the text where it says, ‘I love winning’. And they said, ‘Well, that works perfectly because Tiger says he hates losing’. So that’s a part of it, I suppose. I feel I’m the ‘love winning’ rather than the ‘hate losing’ type.”

“That’s interesting,” I observe, “because it would be easy to consider them to be the same thing.”

“No, I see it in two different ways, but both work.”

“McEnroe said this about you: ‘One of the important things [Federer] has over everyone, and he has it more than any other player I’ve seen since Connors, is his love for the sport. Real love. He loves to be out there, to be around tennis, everything about it . . . There is none of the angst that I had, no demons playing with him’. Can you explain that love?”

“Well, I’m a positive person, a very positive thinker,” he replies. “That’s why I like the more positive approach of ‘I love winning’, because to hate losing, to me, is a bit negative. I guess my love for the sport started as a little boy watching Becker and Edberg facing off in the Wimbledon final. I dreamed about it but I never thought it would happen to me. It’s so difficult to keep winning and to keep your love for the game because of all the travelling and the sacrifices, but I just said, ‘I’m not going to let that happen to me. I’m going to take a positive approach that travelling is great and that I’m going to see different cultures and places I would never see if I wasn’t a tennis player’. My wife loves it. I love it, so ‘let’s have a good time because it’s not going to last until I am 70’. And so far that approach has worked for me.”