A fluid operated actuator (1) comprises a plurality of elongate parallel pressure chambers (6), each chamber comprising a plurality of individual bellows (7) connected end to end through at least one rigid connecting plate (2). Each connecting plate (2) connects a respective two adjacent bellows (7) of each pressure chamber (6) and holds the pressure chambers in laterally spaced relationship at the connecting plate (2). The actuator also incorporates a flexible tensioning member (3) to constrain longitudinal extension of the actuator. In one possible embodiment the tension member is a wire rope ligament aligned with the longitudinal axis (x) of the actuator and attached to the actuator at opposite ends thereof.
