Chester Weir across the river was built in 1093, under the orders of Hugh Lupus, to provide power to water powered mills along the banks of the river, and to improve the navigability of the river, which was still a major trade route at the time. The mills ran a legally enforced monopoly, with all Cestrians being forced to have their corn ground at these mills. The millers were reputed to be lazy and greedy, taking many times what they should in tithes. The song "Miller of Dee" was written about these millers, which led to "Miller of the Dee" becoming an insult in Mediaeval culture, meaning a thief or a cheat.