The Langley smeltmill was built in 1768 by Greenwich Hospital and expanded in the 1770s to include two refining furnaces (for extracting silver from lead ore), a reducing furnace (to convert waste lead into metallic lead) and a slag hearth (for resmelting waste slag from the ore hearths). A second smeltmill was built at Blaghill in the 1780s. Both shared the same flue system, the first section of which was built between 1801 and 1803. By 1805, each smeltmill had three ore hearths, a double refining furnace, a slag hearth and roasting and reducing furnaces. By 1817, zinc was also being smelted at Langley and, although initially successful, it could not compete with competition from Germany and these works closed in 1822. Langley Mill had expanded during this period and between 1845 and 1860 the flue system was also extended. Most of Blaghill Mill seems to have been demolished by about 1860 with some of the remaining buildings being converted into cottages. The last section of the flue system and the chimney were completed by 1882. The smeltmills finally closed in 1887 and much of the works were demolished by 1896. The entire layout of Langley Mill survives as earthworks which together with the Blaghill Mill site, represent a complex lead works of two separate smeltmills. This is a Scheduled Monument and the chimney is also a Grade II Listed Building protected by law.