castle is a fortified building or set of buildings used to provide permanent or temporary protection and accomodation for kings and queens or important noblemen and their families. The term castle usually refers to stone buildings constructed during the Medieval period. The castle provided the centre for political and administrative power for the region.

The term castle can also apply to ancient fortresses and to the towers built at the front and back of Medieval ships from which archers could shoot arrows.

Of the three dangers listed here the threat from civil war or the need to control the population were the main reasons that the majority of castles were built in Europe. Although foreign invasions did occur not many castles can be said to have built because of the fear of foreign invasion. Those that were are on the south and east coast of England such as Dover and Portchester.

During the early years of the tenth century (900-925), the threat from Viking invasion was great and so Edward the Elder and his sister Ethelflead, Lady of the Mercians, organised the fortification of many towns , including Shrewsbury, Bridgenorth, Tamworth and Warwick. What form the fortifications took is not known as no records survive. Stone may have been used where it was available, but most likely it would have been ditches and wooden palisades that surrounded the towns.

Castles became extremely important as a place of safety during the conflicts between rival groups: -

• The king and barons who were upset by his rule.
• Opposing branches of the same royal family.
• Rival barons.

After the Norman invasion of Britain in 1066 the Normans constructed a large number of motte and bailey castles across the country. William the Conqueror and his trusted barons built these castles to control the country's newly subdued inhabitants. William feared an uprising by an unhappy population who outnumbered their Norman conquerors. The castles were required so that the Normans could remain safe and in control.

Major castles were built in or near large centres of population. On the edge of London William the Conqueror had a massive square keep constructed as a reminder to the Londoners that he was their king. Similarly castles were built in Exeter, York and at other important medieval cities. William also built castles at strategic locations such as important river crossings and crossroads.

The Kings of England built many large and imposing fortresses containing private accomodation for themselves and their families. These castles were passed down from generation to generation and were adapted and remodelled to fit the fashions of the period. Their locations were most likely to be politically motivated and built in an important city or at a river crossing, but some were placed in more remote locations for reccreational purposes.