Everyone has a cold, grim estimate. The Smithsonian Ocean says a great white shark can smell a “single drop of blood floating in 10 billion drops of water”. National Geographic Kids puts this acute sense of smell as “one drop of blood in 100 litres of water”.

Two-legged predators, who work in stadiums, have similarly acute ways of sensing vulnerability. Sports’ version of blood in the water is altered body language, hesitant form, errors. When an athlete displays vulnerability, rivals sniff it from a continent away.