The greatest cycle race in the world completed its 113th edition yesterday in Paris. Even people who do not follow the Tour will be familiar with the iconic and much coveted maillot jaune (yellow jersey), the prize for the cyclist who finishes the three-week race quickest. And yesterday Slovenian Tadej Pogačar wrote his name into the history books by winning his ffith Tour de France to equal the all-time record, wearing yellow from day three all the way to the Champs-Élysées.

But from a mathemati...