Royal Armament Research and Development Establishment

Fort Halstead is a research site of Dstl, an executive agency of the UK Ministry of Defence. It is situated on the crest of the Kentish North Downs, overlooking the town of Sevenoaks. Originally constructed in 1892 as one of a ring of fortresses around London, Fort Halstead was to be manned by volunteers in the event of a crisis.

The base became home to the Projectile Development Establishment, the Ministry of Supply and later was the headquarters of the Royal Armament Research and Development Establishment (RARDE).

Fort Halstead formed a part of the London Defence Positions, a scheme devised by General Sir Edward Bruce Hamley and implemented by the Secretary of State for War, Edward Stanhope, who announced the plan to Parliament in 1889. The scheme envisaged a line of entrenchments which would be dug in the event of war to protect the southern and eastern approaches to the capital. Supporting these were to be thirteen simple forts, known as "Mobilisation Centres" which would contain the tools, stores and ammunition for the men of the Volunteer Force, who were tasked with digging the entrenchments and manning them against any invaders.

Putting these plans into action in 1890, the War Office purchased land at Halstead, Kent, on high ground near the town of Sevenoaks. Delayed by a shortage of funds, the polygonal fort was constructed between 1895 and 1897; it featured vaulted barrack casemates on the west side and a magazine on the east. An earthen rampart with positions for light field artillery pieces and machine guns was surrounded by a ditch with a concrete revetment on the scarp face. A cottage was built for a caretaker, who was responsible for maintenance and security in peacetime.

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