Apparatus for providing directional control of bore drilling equipment

According to the invention there is provided an apparatus for providing directional control of bore drilling equipment comprising a hydraulic pump (20) having an input shaft (21) for receiving an input torque from a drill pipe (1) and being connected in use to a drilling head; and control arrangement for varying the rate of fluid flow through the pump. The control arrangement includes a closed loop oil-filled system comprising the hydraulic pump (20) and a main valve (30), wherein oil from the pump is routed through the main valve before returning to a pump input; and an orifice control system (40) which is operable to control the position of the main valve in response to an input signal from a control processor.