A controller for use with a machine comprising a machine body, and a load handling apparatus coupled to the machine body and moveable by a movement actuator with respect to the machine body, the controller being configured to receive a signal representative of the position of the load handling apparatus with respect to the machine body and a signal representative of a moment of tilt of the machine, wherein the controller is further configured to issue a signal for use by an element of the machine including the movement actuator, which in response to the signal issued by the controller, is configured to restrict or substantially prevent a movement of the load handling apparatus when a value of the signal representative of the moment of tilt reaches a threshold value, the threshold value being dependent on the signal representative of the position of the load handling apparatus with respect to the machine body.