William, Duke of Normandy, was the King of England from 1066 – 1087, and he managed to transform the country in that time.
He defeated Harold the king and destroyed the flower of his army at Hastings. After that he set out to build a new England, imposing upon its people his own brand of feudalism.
He made every landowner, even his relatives and friends swear fealty to him.
He instituted the Doomsday Book, a comprehensive survey of the contents of nearly every manor in the land, down to the last sheep and cow.
He kept order throughout his realm, ruling sternly but on the whole with justice.