An external rear view mirror assembly to be fitted to a motor vehicle is disclosed. The assembly comprises: a mirror base mountable to a vehicle; a mirror head frame rotatably mounted to the base for rotation about a mirror head axis; a detent operably interposed between the base and the frame; a spring acting between the frame and the base in a direction parallel to the axis, the spring for holding the detent engaged; and a power fold mechanism operably interposed between the base and the frame, the power fold mechanism having a drive train and a clutch mechanism, the clutch mechanism comprising a pair of axially spaced apart clutching faces, connecting the drive train to the base when the drive train is driving, the clutch mechanism arranged and constructed such that forces are not transmitted from the frame to the drive train when the drive train is not driving.