During the invasion scare of 1588, Southwold was defended by an earthen wall constructed along the cliff, with a 2-gun battery on Gun Hill, and a battery at the north end called the Higham Bulwark, just south of the present boating lake. The defences were ruinous in 1626 when a privateer captured a ship in full view of the town, drove the gun crews from the battery and bombarded the town. (PastScape)
Fort Sussex?–Large moated fort of triangular plan with large quadrangular corner bastions shown on map of 1588(?). Shown as being probably situated in area of present Boating Lake just north of Southwold. According to Eversley (school) boys project on Southwold, the fort was planned as a precaution against the Spanish Armada in 1588 but was never actually built although the source of this information is unknown. The area is marked 'brickfield' on OS 1st edition map, and later as 'boating lake' but the N side and parish boundary, both follow a sharp angular course reflecting part of the fort plan of 1588. (Suffolk HER)
It would seem these defences were started, although it would they may not have been finished. The Fort Sussex name is tentatively given the northern fort by the Suffolk HER - presumably named for the Henry Radclyffe, Earl of Sussex, who was a prime figure in the Armada defenses. A marked kink in the northern parish boundary and course of an waterway is ravelin shaped, in the right location and is suggested as a relic of the forts plan in the Suffolk HER.