Abstract: With reference to FIG. 1, the present invention provides valve operating system for operating a pair of poppet valves (10, 32) of an internal combustion engine. The system comprises a source of pressurised hydraulic fluid (22), a fluid return (23), a first hydraulic actuator (13) which the first poppet valve (10) and a second hydraulic actuator (13) acts on the second poppet valve (32). A first valve (21) is connected to both the source of pressurised fluid and the fluid return (23). A second valve (20) is connected between the first valve (21) and the first hydraulic actuator (13). A third valve (30) is connected between the first valve (21) and the second hydraulic actuator (31). An electronic controller (40) controls operation of the valves (20, 21, 30) to open and close the pair of poppet valves (10, 32).