The Lee was an important waterway from Saxon times. About 1190, the Abbot of Waltham was permitted to make a cut to improve the navigation. In 1424 and 1430, it became subject to the very first Acts for the navigational improvement of any river. More improvements were made in the eighteenth century, which furthered the development of industry along the route. The Lee also provided an important supply of water to London.
Richard Thomas has compiled a very informative website with very comprehensive information on the history of the Rivers Lee and Stort. See the History of the Lee and Stort website.