Medieval England covers the period from the 5th to 14th centuries known as the Middle Ages. This era was defined by the feudal system of rigid social classes and decentralized political and economic power centered around a network of lord and vassal relationships. At the top was the king, followed by powerful lords and lesser lords, with knights and serfs at the bottom. Manors were largely self-sufficient agricultural estates ruled by local nobles. The legend of King Arthur developed over centuries as a symbol of leadership against invaders and a code of chivalry among knights.