A hydraulic tensioning apparatus for tensioning a threaded member (2) having a thread, comprising: a hydraulic tensioner (1), having a body (4) and a pressure space (13) for hydraulic fluid and having a thread engaging member (7) arranged to engage the thread of the threaded member (2) and to be urged away from the body (4) on introduction of hydraulic fluid into the pressure space (13) so as to tension the threaded member (2); a displacement sensor (11, 12) arranged to measure a linear displacement of the thread engaging member (7) relative to the base (4) and to provide an output indicative of the linear displacement; a rotation sensor (65, 66) arranged to determine a rotation of a nut (3) rotating on the threaded member (2) and arranged to produce output indicative of a rotation angle of the nut (3); and a control unit (80) arranged to take as inputs the outputs of the displacement sensor (11, 12) and the rotation sensor (65, 66), and to determine from the output of the displacement sensor (11, 12) a required angle of rotation of the nut (3) which accommodates for extension of the threaded member (2) due to being tensioned by the hydraulic tensioner (1).