evensey Castle is located on the south coast of England and had once been a Roman fort. It is where William the Conqueror landed in September 1066 when he invaded the country. Before marching to Hastings William repaired the castle so that it could be defended and used it as a base to regroup his invasion force. After the Conquest William granted the castle to his half-brother Robert, Count of Mortain. The shape of the castle is unlike other Roman forts which are mostly rectangular. Pevensey castle is oval in shape and the walls follow the contours of the high ground it sits upon. Robert built his castle in the south-east corner of the Roman fort and set about repairing the Roman walls which were 20 to 30 feet high and 10 feet in thickness. The castle was repaired and improved to such an extent that it proved to be hard to capture. It stood up to a siege in 1088 by William Rufus when Robert of Mortain and Odo rebelled against the English King and tried to put Rufus' brother Robert, Duke of Normandy on the throne. The castle only fell when the food ran out.

William, Count of Mortain, Robert of Mortain's son, took possession of the castle but when he rebelled against King Henry I he was stripped of the castle.

In 1147 King Stephen laid siege to the castle when its owner rebelled. As before the castle walls could not be breached and it only fell to the King when the supplies ran out. Pevensey then became the property of the Crown.