Tilbury Fort is the site of a blockhouse built during the reign of Henry VII as part of his Device Fort which included coastal fortifications at numerous sites including Pendennis Castle and two blockhouses to protect the entrance to Milford Haven. It was after the Dutch fleet successfully attacked the Medway in Jun 1667 that the new star shaped fort, with five sides and four bastions, was built. The fort proved difficult to built because of the marshy ground and by 1681 funding had run out.
Nevertheless Tilbury Fort was regarded a strong fortifications with more than a 150 guns by 1715, although many were of dubious quality. By 1715 the Board of Ordnance built two magazine at the Fort able to hold 3,600 barrels of gun powder. Some modernisation was carried out during the Napoleonic Wars but little was done to upgrade Tilbury Fort.
The 1850s saw the introduction of armoured warships and rifled guns requiring general improvements in coastal defences. The Royal Commission on the Defence of the United Kingdom in 1859 regarded Fort Tilbury as being too close to the dockyards given the range of the new rifled guns, and therefore recommended a series of new fortifications further to the East. Fort Tilbury was designated as a second line of defence and in 1868 the north-east and east bastion and the south-east curtain wall was identified as suitable for thirteen 7-inch RML guns behind iron shields. At this time the Fort mounted five 68-pdr SB guns, five 32-pdr SB guns and five 10-inch SB.
In 1888 these guns were upgraded to seven9-inch and one 11-inch RML guns. The old Tudor Blockhouse was destroyed when building these RML emplacements.
In 1905 a battery of two 6-inch BL guns was built on the south-east bastion. On the adjacent bastion emplacement for a battery of four 12-pdr QF guns were also built. The image on the right shows one of the 1905 6-inch guns and the Quick Fire Battery.