Wooden castles were quick to build. A motte and bailey castle could go up quickly, from earth and timber found close at hand, and many early castles were made of wood. Later, castles were built of stone, which made them stronger. From the 1100s some owners rebuilt wooden castles in stone, with a stone keep. A keep was the strong inner tower of a castle. Sometimes the wooden fence around a motte was rebuilt in stone, and this is called a shell keep.

The shape of the keep changed, too. Rectangular keeps had corners that could be undermined, so round keeps began to be built from about 1200. Another idea was the concentric castle, which had two rings of walls, one inside the other. Beaumaris was a concentric castle built by Edward I, with a water-filled moat as an extra line of defence. Sites such as cliffs, marshes and high ground gave a castle natural protection.

Inside the walls, one need could not be left to chance. A castle needed its own well, because water was vital for eating, drinking and washing, especially when under siege. Castles were places where people lived and worked, not only forts. The great hall was the big room where a castle's household and guests gathered for feasts. As the Middle Ages went on, castles became more comfortable, and some were used for courts and offices.

Knights changed over the years as well. Early knights wore mail, armour made of thousands of linked metal rings. By the 1400s knights wore suits of plate armour. Then came a new kind of weapon. When gunpowder and cannon came, castle defences could be damaged more easily, so castles mattered less.

Words to know

• undermined: dug beneath
• keep: inner tower
• timber: wood for building
• siege: long attack