A programme of excavations on and around the keep of Pevensey Castle
established that the fort wall of the late Roman "Saxon Shore" fort was
constructed AD 280-300, very possibly during the usurpation of Allectus.
A deep sequence of "dark earth" built up against the inside of the Roman
fort wall during the Roman and early medieval periods, before and after
the establishment of William I's castle after 1066. A substantial stone
keep and probably the gatehouse and inner bailey were constructed around
1200 and traces of a tower on the outside of the Roman fort wall were
recorded. Substantial later repairs to the inside included the addition
of a tower against the outer face of the (collapsing) Roman wall, the
construction of a garderobe chamber and the re-building of the
north-east tower, probably in the early 14th century. The base of the
now ruinous keep was filled with clay after the 16th-17th centuries,
probably to provide a foundation for cannon to defend the castle against
possible Armada invasion in 1588.