Fortifications and Defences

Portchester has a number of different types of fortifications, which were built at different phases throughout the castle's history.

As Barron explains, it is largely due to the nature of these cleverly designed defences and the skill of those defending the castle that, during the French attack on Portsmouth in 1338, the “longbow defenders were able to drive off the attackers” (1985, p.38), though Portsmouth itself was burned to the ground during this attack and two subsequent attacks in the 1300’s.

The fortifications fell into disrepair in the early 1400’s after Portsmouth became a naval hub, resulting in the decline of the importance of Portchester as a defensive outpost. It was after this time that Portchester Castle began to be used for other purposes.

Please click here to view information about the Outer Bailey itself


There are two main gates to the castle, the Landgate (on the west side) and the Watergate (on the east side). There are also two smaller entrances situated to the north and south of the inner bailey, the latter having been blocked off at some point in the past. 

The Landgate, as with most areas of the castle, has been significantly modified and extended since its original construction by the Romans. Initially, the gate itself was much wider than the one we see today, and “massively defended” (Cunliffe, 1967, p.9). The original Roman walls curved round in towards the inner bailey to form a vast opening at the west end of the outer bailey. A large amount of the Roman Landgate and Watergate were demolished and replaced by much narrower late saxon/early medieval chambers with a gate at either end, presumably to increase security and defence at this end of the castle. This reduced the width of the gates from over 40 feet to around 10-15 feet, as they are today.

The Watergate was designed to “repair a breach formed in the old Roman defences” (Cunliffe, 1967, p.15). This was later extended so that the newer gatehouse protruded from the exterior castle wall towards the east (see photograph). The North and South postern gates were simply small archways. These gates were at one stage linked by intersecting North-South and East-West paths, the latter of which is now surfaced.

- North gate from the north ditch bridge. (Click to Enlarge)
- Landgate as seen from west (Click to Enlarge) - Watergate from outside the fort walls. (Click to Enlarge)


The castle itself consisted of 20 bastions around the outer walls, although there are only 14 still in existence, largely due to undercutting by the sea. Also, several were pulled down over the course of the castle’s history. As Cunliffe explains, “One (no.2) was pulled down soon after 1790, no. 13 was lost at about the same time, no.3 was removed in the eleventh century when the keep was constructed” (1975, p.21).

The initial twenty “are built of coursed flint masonry with walls averaging 5ft (1.5m) thick” (Cunliffe, 1975, p.21), which combined with their frequency around the castle walls suggests a high level of defence of the castle walls and the surrounding ground. When necessary, weapons would have been placed at the top of the bastions, and since they were spread equally around the castle walls, it could be defended from all angles.

- The Western Bastions. (Click to Enlarge) - The ditch surrounding the inner bailey. (Click to Enlarge)


Initially the Romans dug ditches around the majority of the landside of the castle, most of which still remain, though probably not in their original state. Cunliffe suggests in his work on the medieval period of the castle that “After the Norman conquest the ditches were at least partially cleared out” (1977, p.9), suggesting that the Normans saw use in the ditches as a defence mechanism even after they had been left to silt up.

The moat inside the walls surrounds the inner bailey and associated Gatehouse (early twelfth century), and was probably constructed later than those dug by the Romans. In all cases these serve as another method of defence, which when combined with the other defences would have made the castle a more impenetrable fortress should invasion ever occur.