Trostrey Weir on the River Usk was partly constructed on shingle banks in the river, and directed water to Gorrats Mill on the left bank. It is named on all three editions of the 25-inch O. S. maps, but its purpose is not indicated. The 2nd edition map of 1901 describes the mill as "in ruins"; nevertheless the outline of the building is still shown on modern maps.
W J Crompton, RCAHMW, 21 April 2011.