Pevensey Bay, United Kingdom

When the Roman army left Britain, the province was more vulnerable to attack, first by the Jutes in east Kent, and the Romanised native Britons attempted to defend their island from attack. Following the Jutish example the Saxons began invading Britain in earnest. Around 491, Saxons, possibly led by Ælle of Sussex began to colonise the south coast and besieged Anderitum over a number of years. After a long struggle the British defences were overrun. Some remaining Britons on the south coast fled north, others emigrated by boat to what is now called Brittany and the area became the Kingdom of the South Saxons, later called Sussex. The old Roman fort of Anderida was burned and left derelict. For a while the ruined castle was known by the Saxons as Andredceaster and the Weald of southern England – which stretches 120 miles (200 km) from Anderida to Dorset – was named Andredsweald, the Forest of Anderida.

The fort probably remained derelict until, in 1042, Harold Godwinson, later Harold II of England, established a stronghold here, improving fortifications by digging ditches within the walls of the fort. The English army remained at the fort during the summer of 1066 before abandoning it to meet the invading Norwegians further north.

When William the Conqueror invaded Sussex in September 1066 there were no defenders at Pevensey and the bay provided a safe haven for the invading fleet.

In late 1066 the Roman fort at Pevensey was occupied by the Normans; much of the Roman stonework still existing today is due largely to the work of Robert, Count of Mortain (half brother to William), who was granted Pevensey Castle shortly after the Norman Conquest. Robert de Mortain used the remains as the base for building his castle, carrying out only minor repairs to the walls forming the outer bailey, and building a new inner bailey at the eastern end.

At the time of the Domesday survey of 1086, Pevensey was a significant settlement of 110 households and a mill.

The castle was besieged several times during the 11th–13th centuries. An order by Queen Elizabeth I that it be demolished and an attempt at demolition during the Puritan times were both unsuccessful: the order was ignored and only a few stones were removed on the two occasions. As late as 1942 small additions were made to the castle for the defence of Britain, when it was used to spot German aircraft during World War II.

The Liberty (or Lowey) of Pevensey was an ancient now obsolete hundred, containing the parishes of Westham and Pevensey. They were entirely within the Levels and together regarded as constituting part of the port of Hastings, and consequently would be entitled to all the privileges and immunities enjoyed by the Cinque Ports and not part of the county of Sussex jurisdiction. This would have been the case until the system of hundreds as administration divisions was abandoned in the 19th century.

In the 16th century Pevensey became what was known as a "non-corporate limb" of the Hastings, as part of the Confederation of the Cinque Ports. Along with most of the other Ports, its importance dwindled as the ports themselves became disconnected from the sea: Pevensey was two miles (3.2 km) distant.

During the 18th and 19th centuries Pevensey Bay became involved in the south coast smuggling trade, since it was one of the easier places to land the contraband. In 1833 a violent clash occurred between the smugglers and customs men at Pevensey Bay.

Some of the more than 100 Martello towers were erected along the beaches of Pevensey Bay at the beginning of the 19th century to guard against Napoleonic attack.