Fort Hubberstone, on the west side of Milford Haven, Pembrokeshire, is a Grade II* Listed Building which belongs to a series of forts built as part of the inner line of defence of the Haven following the Royal Commission on the Defence of the United Kingdom. Together with Popton Fort on the opposite shore, it provided an interlocking field of fire, and represented the last layer of defence before reaching the Royal Naval dockyard at Pembroke Dock. Construction began in 1860 and was completed in 1863 at a cost of £55,000. It is a large battery, with eleven guns in casemates, eight in an open battery above, with another nine in an open flank battery, and a large barracks to the rear. It is a D-shaped structure, with a bomb-proof roof which protected the barracks and other buildings from mortar projectiles. On its landward side, it was protected by a deep ditch, and on the seaward side by a counter-scarp gallery. The associated casemate battery is located further down the headland and separated from the fort.