An actuator release mechanism comprising a longitudinal member, e.g. a piston, which is moveable axially to permit or prevent axial movement of the lock bolt and hence deployment of the actuator. Movement of the piston is due to the force of the lock bolt, under a spring force, on the one hand, and to the position and force of a linkage assembly on the other hand. The linkage assembly comprises a first link fixed, at one end, e.g. by means of a piston lock pin, to the piston and fixed at a pivot point to a second link. The second link is fixed to a rotational drive means, here a rotary solenoid or stepper motor, so as to rotate about a centre of rotation.