had two faces forming an angle towards the river, while the second smaller battery had a straight front. It was protected on the riverside by a flat-bottomed ditch within which was a pallisade made of timber standing about high. The two batteries were armed with fifteen heavy guns (24 and 32 pdrs.) which fired through embrasures. Milton Chantry was incorporated into the fort's perimeter and was converted into an artillery barracks. By the 1790s, additional buildings had been constructed, including quarters for the commanding officer, stables and magazines. The rear of the fort was originally open, but by the end of the 18th century a defence wall and caponier with loopholes for muskets had been built to close it off. A kiln was also built to heat shot to a red heat for setting ships on fire. 19th century reconstructions During the 19th century, New Tavern Fort underwent major reconstructions, though it retained its basic plan and earthworks. The gun emplacements were modernised in 1848 to install platforms for traversing guns, and further magazines were built. Further upgrades were soon needed. By the end of the 1850s, Britain and France were engaged in a naval arms race. A new class of ironclad ships with powerful rifled muzzle loader (RML) guns, exemplified by the British HMS Warrior and the French La Gloire, posed a substantial threat to existing coastal defences. In response, the British government established a Royal Commission on the Defence of the United Kingdom to review the defences and make recommendations on improvements. Noting the importance of the Thames and its vulnerability to seaborne attack, the Commission advocated in its report in 1860 that two principal lines of defence should be established along the Thames. Three forts would be constructed or rebuilt - Shornemead Fort and Cliffe Fort in Kent and Coalhouse Fort in Essex - to provide an outer line of defence, with further forts and batteries protecting key sites further downriver. The inner line of defence would be provided by Tilbury Fort and New Tavern Fort. The fort underwent one more rearming before the Commissioners' recommendations were put into effect. Its existing guns were replaced in 1859 by ten 68-pounder guns, among the most powerful smooth-bore guns in service at the time, with a range of up to . Two of the 68-pdrs. were replaced by 1865 with a pair of 10-inch shell guns, with a further