The decision to build the redoubt was made at a conference held in Rochester on 21 October 1804, to discuss defence against Napoleon's planned invasion of the United Kingdom, preparations for which were gaining momentum on the opposite side of the English Channel. The meeting, which was attended by the Prime Minister, William Pitt the Younger, agreed to adopt a revolutionary scheme to build a chain of mutually-supporting circular artillery towers along a stretch of the Channel coast where the French were thought to be most likely to land. The scheme had been devised by Captain William Henry Ford of the Royal Engineers and championed by Brigadier-General William Twiss who commanded the Royal Engineer Southern District. The original plan called for 83 Martello towers, each mounting a single heavy gun, at intervals along the coast and three 11-gun towers at Sea Houses (Eastbourne), Rye Harbour and Dymchurch. In the event, 74 Martello Towers were actually built and plans for the 11-gun tower at Rye were abandoned. The 11-gun towers, which came to be known as "circular forts" or "grand redoubts", were intended to act as barracks and stores depots for the rest of the Martello chain, as well as formidable fortresses in their own right. A third redoubt was later constructed at Harwich in Essex to support the Martello chain built to defend the east coast; although broadly similar, it differs in some details from the south coast redoubts.