Fort Halstead has played a significant role in British Military history, first as part of a late 19th century plan to protect London from invasion, with fortifications (mostly earthworks) as illustrated below. The reasons for fearing invasion war were relatively short-lived, and its intended use as a defensive structure lasted less than a decade.
It’s more famous albeit secretive use, as a national centre for research and development of munitions and explosives, expanded rapidly during the first half of the 20th century, with important military programmes such as the development of components for UK’s first nuclear bomb. The 21st century will see the whole site return to non-military use.
Fort Halstead’s late-19ct century origin is quite surprising. Who would have thought that at that time Britain’s government gave serious consideration to the threat of a land invasion? And not just think about it, but to actually develop a London Defence Scheme involving construction of a string of defensive forts along a 70 mile stretch of the North Downs? The plan was put into effect in 1895, with the construction of emplacements located at natural strongpoints along the top of the escarpment. Positioned at approximately 5 mile intervals, the idea was that, in the event of an outbreak of war, these emplacements could be rapidly linked with trenches and other defensive earthworks!
The map below opposite shows this line of forts and associated military barracks. Most of the ‘forts’ were nothing more than earthworks, designed to function as mobilisation centres and to hold munitions and other supplies. Fort Halstead, however, was one of the more elaborate installations, with artillery positions and machine-gun emplacements making it ready it to take part in defensive action.
The strategic value of Halstead Fort’s location can be seen from the topographical map below. The road from Hastings to London originally climbed the escarpment via Star Hill, immediately to the west of Fort Halstead, but in the eighteenth century demands for easier passage of horse-drawn haulage favoured a new Turnpike road with an easier gradient. This new road turned east at the foot of the escarpment along the alignment of Pigrims Way, then following the contours eastward up to Polhill, taking much the same route as the existing A224.
Halstead Fort sits in a commanding position immediately above these two routes. By the end of the 19th century a railway line had been added, so Fort Halstead sat on top of three transport routes and, perhaps equally importantly, overlooked the Darenth Valley itself, as it cuts through the North Downs on its way to Dartford.
Fort Halstead didn’t of course see military action of any type. By 1906 the Royal Navy took possession of its latest, world-beating generation of battleships, the Dreadnoughts, and the idea of anyone landing an army on the south coast of England faded away for the time being, taking the London Defence Scheme with it but leaving behind a military asset at Fort Halstead.