A fastener (200) having a head (202) comprising a recess (206) for receiving the driving portion (12) of a driver (10), the driving portion and the recess being shaped such that rotation of the driving portion within the recess engages the driving portion with the head, such that further rotation of the driver causes the fastener to rotate, wherein the recess in the head of the fastener is tapered in the longitudinal axis of the fastener, such that the recess is widest at its furthest point from the surface of the head of the fastener, and wherein the recess further comprises one or more lateral tapers extending in a direction transverse to the longitudinal axis of the fastener.