An apparatus comprising a prime mover and a plurality of hydraulic actuators , a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and comprising a plurality of working chambers having a volume which varies cyclically with rotation of the rotatable shaft, a hydraulic circuit extending between a group of one or more working chambers of the hydraulic machine and one or more of the hydraulic actuators, each working chamber of the hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold , the hydraulic machine being configured to actively control at least the low-pressure valves of the group of one or more working chambers to select the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume, and thereby the net displacement of hydraulic fluid by the group of one or more working chambers, responsive to a demand signal , characterised by the apparatus comprising a prime mover speed governor operable to regulate the prime mover speed responsive to a prime mover control signal, wherein the apparatus is configured to regulate the prime mover control signal by feedforward of a signal related to a torque demand, wherein the apparatus is configured to regulate the prime mover control signal to cause the prime mover speed governor to increase the applied torque of the prime mover and then to subsequently, after a delay period, regulate the demand signal to increase the displacement of working fluid and the torque exerted by the group of one or more working chambers , such that the increase in torque exerted by the one or more working chamber 2-is applied concurrently with the increase in torque of the prime mover . each working chamber of the hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold , the hydraulic machine being configured to actively control at least the low-pressure valves of the group of one or more working chambers to select the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume, and thereby the net displacement of hydraulic fluid by the group of one or more working chambers, responsive to a demand signal , characterised by the apparatus comprising a prime mover speed governor operable to regulate the prime mover speed responsive to a prime mover control signal, wherein the apparatus is configured to regulate the prime mover control signal by feedforward of a signal related to a torque demand, wherein the apparatus is configured to regulate the prime mover control signal to cause the prime mover speed governor to increase the applied torque of the prime mover and then to subsequently, after a delay period, regulate the demand signal to increase the displacement of working fluid and the torque exerted by the group of one or more working chambers , such that the increase in torque exerted by the one or more working chamber 2-is applied concurrently with the increase in torque of the prime mover . <EOS>