Tennis has the unusual distinction of contributing to the deaths of not one but two European monarchs. The first was King Louis X of France (he was actually history’s first recorded tennis player): In 1316, he caught a chill after an exhausting game, developed pneumonia, and died.
The second was King James I of Scotland: On February 20, 1437, while fleeing a mob of 30 assassins, James escaped through a sewer tunnel beneath his house only to find its exit blocked off. Days earlier, he had ordered his servants to seal the exit because he kept losing his tennis balls down there. His assassins caught up to him and stabbed him to death.