the French military engineer Montalembert, in a novel move away from the bastioned trace design used in other British forts of the time. It was an open battery like the first fort, but with much more numerous and powerful artillery – thirteen 32-pdr. guns on traversing carriages, each with a range of . The ramparts occupied three sides of the fort, facing the river. A barracks was constructed on the remaining two (landward) sides, along with bomb-proof magazines and defensive caponiers to flank the fort's ditch. The marshy ground caused major problems and the fort was not completed until 1853. Subsidence badly cracked the cookhouse and barracks, and one of the caponiers split away from the rest of the structure. By the late 1850s, Britain and France were locked in an arms race. A new generation of increasingly accurate and powerful guns had been developed (of the Rifled Muzzle Loader (RML) and Rifled Breech Loader (RBL) types), mounted on fast-moving, manoueuvrable steam-powered ironclad warships such as the French La Gloire and the British . Britain's coastal defences had not been substantially upgraded since the Napoleonic Wars and the country's existing fortifications were largely obsolete. The Thames possessed several naval installations of great importance, including the victualling yards at Deptford, the armaments works of Woolwich Arsenal, the shipbuilding yards at North Woolwich, and the magazines at Purfleet. It was not possible for large warships to reach central London, as the river was not yet deep enough to take ships of more than 400 tons above Deptford. As the American Civil War soon showed, it was quite possible for the warships of the day to run past forts and attack up coastal rivers. The government's response was to appoint a Royal Commission on the Defence of the United Kingdom, which published a far-reaching report in 1860. It recommended that a triangle of forts should be established on the lower Thames, east of Gravesend. This would involve replacing the old Coalhouse Fort on the Essex shore with a new fortification, similarly replacing the existing Shornemead Fort and building a wholly new fort at Cliffe. The location of the forts would enable interlocking arcs of fire from their guns. It was originally intended that the forts would form part of a line of defences running all the way to Chatham, but the rest of this chain was never built. Shornemead was regarded as being