A fastener comprising: a fastener body orientated about a central axis (x-x); said fastener body having a tool-engaging portion to which a driving torque may be applied and a threaded fastening portion configured and arranged to mate with a corresponding threaded element; said fastener body having a shroud-receiving body portion orientated about said central axis; characterised by a shroud concentrically mounted in said shroud-receiving body portion and having an outer surface facing an inner surface of said shroud-receiving body portion; said shroud being supported in rotatable relationship with said shroud-receiving body portion such that said shroud will rotate about said central axis relative to said fastener body under an applied external torque prior to said fastener body rotating when said fastener body is engaged with an external structure at a design installation torque, said shroud comprising an outwardly extending annular shoulder ; said shroud-receiving body portion comprising an inwardly deformed stop (40,140 240, 340) radially overlapping said outwardly extending annular shoulder of said shroud; and said deformed stop of said shroud-receiving body portion and said annular shoulder of said shroud forming a shroud-retaining element restraining said shroud from movement in at least a first axial direction along said central axis and permitting said shroud to rotate about said central axis relative to said fastener body under an applied external torque prior to said fastener body rotating when said fastener body is engaged with an external structure at a design installation torque. a fastener body orientated about a central axis (x-x); said fastener body having a tool-engaging portion to which a driving torque may be applied and a threaded fastening portion configured and arranged to mate with a corresponding threaded element; said fastener body having a shroud-receiving body portion orientated about said central axis; characterised by a shroud concentrically mounted in said shroud-receiving body portion and having an outer surface facing an inner surface of said shroud-receiving body portion; said shroud being supported in rotatable relationship with said shroud-receiving body portion such that said shroud will rotate about said central axis relative to said fastener body under an applied external torque prior to said fastener body rotating when said fastener body is engaged with an external structure at a design installation torque, said shroud comprising an outwardly extending annular shoulder ; said shroud-receiving body portion comprising an inwardly deformed stop (40,140 240, 340) radially overlapping said outwardly extending annular shoulder of said shroud; and said deformed stop of said shroud-receiving body portion and said annular shoulder of said shroud forming a shroud-retaining element restraining said shroud from movement in at least a first axial direction along said central axis and permitting said shroud to rotate about said central axis relative to said fastener body under an applied external torque prior to said fastener body rotating when said fastener body is engaged with an external structure at a design installation torque. <EOS>