 In 1899 it was noted that the castle was being used to store dry guncotton (a highly-flammable and dangerous explosive), while the less dangerous 'wet guncotton' form was kept on board the ever-present hulks moored nearby.This practice ceased soon afterwards, specialist storage magazines having been built alongside Chattenden at Lodge Hill.After the First World War, Upnor became a Royal Naval Armaments Depot (RNAD), one of a group of such facilities around the country.