The present invention (with reference to FIG. 1) is an arrangement of an internal combustion engine poppet valve and a hydraulic actuator therefor comprising: an actuator housing (16); spring means (104,105) for biassing the poppet valve (101) into engagement with a valve seat therefor; a first piston (1) of a first cross-sectional area slidable in a first chamber formed in the actuator housing (16), the first piston (1) having a passage therethrough for the flow of hydraulic fluid; and a second piston (15) of a second cross-sectional area smaller than the first cross-sectional area slidable in a second chamber formed in the actuator housing (16), the second chamber opening on to the first chamber; wherein: the first chamber is connectable to a pressurised hydraulic fluid supply line and to a hydraulic fluid return line; and the second piston has an upper surface (110) engageable by a lower surface of the first piston; and the first piston is configured without a passage which is both aligned with the second piston and which has a portion of constant cross-sectional area greater than the said second cross-sectional area.