Pevensey was the location of a Roman fort called Anderitum which was one of eleven forts between Essex and the Ise of Wight built to defend against the Jutes and Saxons in the 4th century. The forts were known as Saxon Shore Forts.
The fort was later burnt down by the Saxons after the Romans left and was probably derelict until 1042 when a stronghold was built there.
There are no exact remains of the Roman fort left although roofing tiles have been found mixed in with the current foundations.
see Roman Britain