The bastion on Gunners Walk was thought to contain a mill, but a resurvey of the area in the 1980s suggests that there was never a mill at this site. The irregular shaped bastion contains a narrow walk alongside the walls which surrounds a paved area below water level and a narrow channel between the moat and dock. The narrowness of this channel (0.83m wide) makes it unlikely that this could have been a mill. The sluice mechanism at the E end of the channel was most probably used to regulate the level of the moat.
(Source: Site File AN/Defence/SH67 from notes by A.J. Parkinson)
J Hill 15/04/2004

Part of castle (NPRN 95769).