On Friday, Roger Federer, at the age of thirty-six, became the oldest world number one in the history of tennis. He first claimed this spot an astonishing fourteen years ago. Such supremacy, and such longevity, is rare, not just in sport but also in business, politics, and just about everything else. The way he’s done it is even rarer. As a young child, I always liked tennis, but I liked lots of other sports too.