West wall Postern\Sally Port
Situated at the far Southern end of the castle enclosure, the sally port, or West wall postern, offered safe access from within the confines of the castle's outer court to the South Steel Battery.
The Battery was originally built in 1643 to provide clear line of site for a set of guns to cover the town's harbour. The postern was broken through the wall at this point, and designed to give gunners safe access to the gun platforms here. This is basically a covered staircase set with gun loops.
Typically I didn't realise the importance of this structure when I visited this year, so didn't go down into the covered walk way within the wall to take more photos. This is one of two posters set within the West walls, the second sited a short distance to the North and set between two towers for protection.