Like most countries in the Middle Ages, England was a monarchy - it was ruled by a king. And the king needed to be strong. But not all kings were strong enough. King Stephen, William I's grandson, spent most of his reign fighting a civil war against his cousin Matilda.
The earls and barons had their own castles and armies of knights and archers. In Stephen's reign, some fought for the king, and some fought for Matilda. Most of the time, they did as they liked. The worst of them robbed and tortured the English peasants and burned their homes.
When Stephen died, Henry II, Matilda's son, became king. Henry was only 21 years old. He was good-looking, tough, and fond of sport. He was also a wise and brave ruler. He was not afraid of the great lords, and had made up his mind that there would be no more civil war.
When he was in England, Henry travelled far and wide, making sure that there was peace, law, and order in the land. He sent his judges round the country, so that accused persons would get a proper trial. He made all the lords and knights swear to obey him, their king.
Walter Robson: Medieval Britain; Oxford University Press, 1991/2000, page 11 f.