Since at least the Norman Conquest, the Tillingbourne River has powered numerous mills that were initially used for processing commodities such as grain and wool. Gunpowder first began to be produced alongside the river in Chilworth by the East India Company in 1626, using saltpeter from India, sulfur from various volcanic regions, and charcoal produced locally. Production continued for the next three hundred years. Nature has long since returned to the works, now a haven for protected species such as dormice and bats. The site is faced with several challenges though, including phosphate enrichment of the Tillingbourne and ash dieback.