Fort Halstead was 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, southeast of London. Originally constructed in 1892 as part of a ring of fortresses around London, Fort Halstead was to be staffed 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).