A control mechanism comprises an elongate handle 10 having an external thread 12 and a barrel 20 with internally projecting pins 21 threaded over handle 10. Rotation of barrel 20 causes handle 10 to move back and forth along its longitudinal axis to retract and advance a catheter sheath to which handle 10 is coupled, thereby enabling an implant to be deployed by the catheter. Rotation movement of barrel 20 and longitudinal movement of handle 10 can be disassociated to enable speedy retraction or advancement of the catheter sheath.
