" King Alfonso of Castile, who was besieging the Muslim stronghold, was urged to flee to safety. However, the king, who had lost a future daughter-in-law to the plague two years earlier—Princess Joan of England—insisted on remaining with his army. On March 26, 1350, a Good Friday, Alfonso became the only reigning European monarch to die of the pestilence. "

― , The Great Mortality: An Intimate History of the Black Death, the Most Devastating Plague of All Time