The Medway and its tributaries and sub-tributaries have been used for over 1,150 years as a source of power. There are over two hundred sites where the use of water power is known. These uses included corn milling, fulling, paper making, iron smelting, pumping water, making gunpowder, vegetable oil extraction, and electricity generation. Today, there is just one watermill working for trade. Those that remain have mostly been converted. Such conversions include a garage, dwellings, restaurants, museums and a wedding venue. Some watermills are mere derelict shells, lower walls or lesser remains. Of the majority, there is nothing to be seen. A large number of tributaries feed into the River Medway. The tributaries that powered watermills will be described in the order that they feed in. The mills are described in order from source to mouth. Left bank and right bank are referred to as though the reader is facing downstream. This article covers the watermills on the tributaries that feed in below Penshurst and above Yalding. The Southborough Bourne A stream rises in Colebrook Park, Pembury, and enters the Medway from the left below Town Mills, Tonbridge. Anciently known as the Calverley Stream, it powered three watermills. Vauxhall (Bourne Mill) Furnace, Southborough The location of this furnace is near Mote Farm, Southborough. Iron smelted here was worked at the forge downstream. The forge was in operation from 1552, when it was owned by the Duke of Northumberland and Robert True was the ironfounder. Late in 1552, the Duke leased the furnace for 40 years to Sir George Harper and Thomas Culpeper, with permission to build another furnace and forge. Culpeper quit the lease in 1571 and in 1573 David Willard was working for Sir Thomas Fane. In 1588, Edmund and Abraham Willard were ironfounders at Bourne Mill Furnace, most likely to have been Vauxhall. The ironworks were mentioned in leases of 1622 and 1678, but appear to have been idle in 1653 and 1664. A powder mill was erected here in 1771. A few remains of the waterwheel were on site in 1933. The dam has been measured at long and high. Brook (Broakes, Old Forge) Mill, Southborough David Willard built this forge for Sir Thomas Fane in 1553. It was a forge in 1574 and worked in conjunction with Vauxhall Furnace from 1623 to 1679. It was a Pestle mill in 1763. It was a gunpowder mill from