Perhaps the most striking of all the Haven forts, sitting remote on a mid-channel rock, Stack Rock was first developed in 1852 as a trefoil-plan battery similar to the north-east Martello Tower at Pembroke Dock. It was one of a chain of forts designed to defend the middle part of Milford Haven and the Royal Naval Dockyard at Pembroke Dock against an invasion from France under Napoleon III. It was later extended in 1870; an entirely new building enveloped the former tower within. In its day Stack Rock was armed with sixteen 18-ton Rifled Muzzle Loading (RML) guns, and manned by 150 men.

T. Driver, RCAHMW, 17 July 2008.