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 , wherein the apparatus comprises a machine controller which is operable to apply a torque limit to the hydraulic machine, the hydraulic machine torque limit being selected to be below a prime mover torque limit in dependence on a current prime mover speed, and wherein the hydraulic machine controller is further operable to cause the hydraulic machine to implement one or more rates of change of torque comprising a first rate of change of torque and a second rate of change or torque, and the hydraulic machine controller is operable to cause the hydraulic machine to implement the first rate of change of hydraulic machine torque when the prime mover is operating below an additional temporary torque limit and the second rate of change of hydraulic machine torque when the prime mover is operating at or above the additional temporary torque limit. 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 , wherein the apparatus comprises a machine controller which is operable to apply a torque limit to the hydraulic machine, the hydraulic machine torque limit being selected to be below a prime mover torque limit in dependence on a current prime mover speed, and wherein the hydraulic machine controller is further operable to cause the hydraulic machine to implement one or more rates of change of torque comprising a first rate of change of torque and a second rate of change or torque, and the hydraulic machine controller is operable to cause the hydraulic machine to implement the first rate of change of hydraulic machine torque when the prime mover is operating below an additional temporary torque limit and the second rate of change of hydraulic machine torque when the prime mover is operating at or above the additional temporary torque limit. <EOS>