A power actuator for shifting a vehicle door lock or other closure mechanism selectively between a locked condition and an unlocked condition by powered operation while also permitting manual operation with the actuator providing indexing of manual shifting between said conditions comprising: a) an operatively fixed housing; b) a motor driven driver annulus journalled in or on said mounting for powered rotation and having interior control formations, a first set of said formations being within first axial zone of the annulus and including spaced radially extending control notches separated by peripheral control lands, and a second set of said formations being within a second axial zone of the annulus and including a plurality of angularly spaced radially inwardly projecting camming lobes, each lobe being diametrically opposite but axially offset from a respective notch; c) an elongate index element movable within the annulus, a head part of said element carrying a drive formation co-acting with the second set of formations to transmit drive angularly displacing said element on powered rotation of the annulus and to provide said indexing by angular movement of said element relative to the stationary annulus during manual operation, and a tail part of said element carrying stop formation co-acting with the second set of control formations to regulate the displacement of the element relative to the annulus; and d) an output element coupled to the index element and to the mechanism in use to transmit one motion to the other characterised in that the tail part of the index element also carries a control projection co-acting with a control slot of the mounting extending radially of the axis of rotation of the annulus, said projection being offset further from head part of the index element than the stop formation whereby the index element can swing angularly about the axis of said projection but its tail part is otherwise constrained for displacement radially of the annulus only with the offsetting providing leverage through the stop formation to ensure appropriate alignment of interacting parts of the element and annulus in operation.