A segment for supporting electromagnetic coupling elements of a stator or rotor of an electrical machine, comprising: a plurality of elongate laminations which are stacked in a first direction to form a lamination stack with elongate edges of the laminations defining opposite first and second major faces of the lamination stack; and a plurality of elongate compression devices passing internally through the lamination stack in the first direction and arranged to compress together the laminations in the lamination stack, wherein: each elongate compression device is in an elastically extended condition thereby generating a compressive force applied to the lamination stack, each elongate compression device is, in relation to the part of the elongate compression device extending through the lamination stack, elastically extended by at least 0.5%, or 1%, or 1.5%, or 2%, or 2.5 %, or 3%, or 3.5%, or 4%, relative to the elastically unextended length of that part, and each elongate compression device comprises: a central rod portion (169, 180, 185) having first and second ends; and first and second anchor portions (170a; 170b) at respective ones of the first and second ends of the central rod portion; wherein each anchor portion is of larger diameter than the adjacent part of the central rod portion; each elongate compression device further comprises: first and second collars (176, 182) fitted to respective ones of the first and second anchor portions, wherein each collar comprises a first piece and a second piece; and wherein each anchor portion has a shoulder for applying a compressive force to the lamination stack. a plurality of elongate laminations which are stacked in a first direction to form a lamination stack with elongate edges of the laminations defining opposite first and second major faces of the lamination stack; and a plurality of elongate compression devices passing internally through the lamination stack in the first direction and arranged to compress together the laminations in the lamination stack, wherein: each elongate compression device is in an elastically extended condition thereby generating a compressive force applied to the lamination stack, each elongate compression device is, in relation to the part of the elongate compression device extending through the lamination stack, elastically extended by at least 0.5%, or 1%, or 1.5%, or 2%, or 2.5 %, or 3%, or 3.5%, or 4%, relative to the elastically unextended length of that part, and each elongate compression device comprises: a central rod portion (169, 180, 185) having first and second ends; and first and second anchor portions (170a; 170b) at respective ones of the first and second ends of the central rod portion; wherein each anchor portion is of larger diameter than the adjacent part of the central rod portion; each elongate compression device further comprises: first and second collars (176, 182) fitted to respective ones of the first and second anchor portions, wherein each collar comprises a first piece and a second piece; and wherein each anchor portion has a shoulder for applying a compressive force to the lamination stack. each elongate compression device is in an elastically extended condition thereby generating a compressive force applied to the lamination stack, each elongate compression device is, in relation to the part of the elongate compression device extending through the lamination stack, elastically extended by at least 0.5%, or 1%, or 1.5%, or 2%, or 2.5 %, or 3%, or 3.5%, or 4%, relative to the elastically unextended length of that part, and each elongate compression device comprises: a central rod portion (169, 180, 185) having first and second ends; and first and second anchor portions (170a; 170b) at respective ones of the first and second ends of the central rod portion; wherein each anchor portion is of larger diameter than the adjacent part of the central rod portion; a central rod portion (169, 180, 185) having first and second ends; and first and second anchor portions (170a; 170b) at respective ones of the first and second ends of the central rod portion; wherein each anchor portion is of larger diameter than the adjacent part of the central rod portion; each elongate compression device further comprises: first and second collars (176, 182) fitted to respective ones of the first and second anchor portions, wherein each collar comprises a first piece and a second piece; and wherein each anchor portion has a shoulder for applying a compressive force to the lamination stack.