South Walls and Monastic Reredorter
When walking round the outside of the castle it is evident that the sea has inflicted a great deal of damage to the castle and it's surroundings.
The two bastions on the south of the Watergate have been lost, (a bastion is a tower or outwork normally projecting out at the base of the wall which provides cover for defenders when warding off attackers). A building of unknown date once stood against the outside of the east wall towards the corner. Round the corner on the south side of the structure the drains from the monastic reredorter (lavatories) can be plainly seen in the wall.
The south wall of the fort and its bastions preserve some of the best examples of Roman work, clearly distinguishable from the medieval work. Where the coastline turns away from the fort the Roman ditch has been dug out; on the west side an outer ditch also existed. In the centre of the wall was the south postern (entry to the castle/fort), which was completely blocked up in Roman times.