Their descendants were members of the Beaufort family, which played a major role in the Wars of the Roses. Henry VII, who became King of England in 1485, derived his claim to the throne from his mother, Margaret Beaufort, who was a great-granddaughter of Gaunt and Swynford. His legal claim to the throne, therefore, was through a cognatic and previously illegitimate line. Henry's first action was to declare himself king "by right of conquest" retroactively from 21 August 1485, the day before his army defeated King Richard III at the Battle of Bosworth.