An actuator comprises a series of elements 414 each pivoted to the next and a housing 400 accommodating at least part of the series of elements with one end of the series projecting freely beyond an exit 404 of the housing. The elements 414 are guided to follow a curved path to the housing exit 404 and are driven along the path by a drive mechanism 412 to vary the total length of elements projecting beyond the exit. The projecting elements are maintained in linear alignment in a substantially rigid, self-supporting column 440 by a toothed belt 426 which progressively engages the elements 414 as they emerge from the housing exit 404.
