The actuator has an elongate body (2) with a longitudinal bore receiving a piston. An endless flexible belt (8) extends longitudinally of the body and is held by supports attached to the body adjacent to the ends about which the belt can pass. A first connector couples the piston rod to the belt. A second connector couples the flexible drive belt to a mounting (6) which slidably supports the actuator body. Linear movement of the piston upon application of pressure fluid causes a corresponding linear movement of the drive belt and thus a movement of the body.
