What sport is called sports of kings?
From the late 1100s The Sport of Kings was, and still is, horse-racing
For some vague reason some people in America suggest that it is Polo; Maybe because some of the recent royal males have been polo players.
Polo was not even known by Europeans until about the 1830s, when the British in India took it up from the Indians, where is was played in Manipur. It originated about 500 BCE in Persia and was migrated right across to China and India.
Horse racing was the sport of at least the following list of British Monarchs: Richard I, Henry VIII, Queen Elizabeth I , James I, Charles I , Charles II, Edward VII, Queen Elizabeth II