Two Electrical Resistivity Tomography survey transects were undertaken over a castle motte at land at Hamstead Marshall, West Berkshire. The surveys were conducted to meet specific research questions concerning the structure of the mound following a geotechnical investigation which appeared to locate a large void from within. The surveys were conducted in single lines across the mound, at approximate right angles. Traverse 1 measures 121m in length as a NNW orientation. Traverse 2 measures 105m, at a WNW orientation. Both traverses begin from outside the mound and associated ditch, continue over the entirety of the mound, and finish off the mound and ditch at the opposite side.