A cutting insert comprising: opposing top and bottom surfaces; a peripheral side surface extending between the top and bottom surfaces, the peripheral side surface comprising opposing first side surfaces connecting to opposing second side surfaces, each of the first side surfaces and the second side surfaces comprising at least one abutment surface portion (21, 23) suitable for seating the cutting insert; a top peripheral edge formed between the peripheral side surface and the top surface, the top peripheral edge comprising: opposing first edges at the intersection of the first side surfaces with the top surface; opposing second edges at the intersection of the second side surfaces with the top surface, the two opposing first edges extending transversely to the two opposing second edges; a first pair of diagonally opposed first corner edges, each first corner edge defined between a leading end of a first edge and an associated second edge; and a second pair of diagonally opposed second corner edges, each second corner edge defined between a trailing end of the first edge and an adjacent second edge; a symmetry axis extending through the opposing top and bottom surfaces about which the insert has a 180° rotational symmetry; a first axis perpendicular to the symmetry axis and extending generally parallel to the first edges in a top or bottom view of the cutting insert; a second axis perpendicular to both the symmetry axis and to the first axis, the second axis extending along the second side surfaces and being transverse to the first side surfaces; characterised in that in a top view of the cutting insert, relative to an imaginary first edge tangent line A' - A' that is parallel to the first axis and contains a first edge tangent point of the first edge proximate an associated first corner edge, each first edge converges inwardly at a first angle (α) towards the first axis and in a direction of an associated second corner edge; and each of the at least one abutment surface portions (21, 23) is spaced apart from its associated first or second edge (15, 17) and has an orientation which is independent of an orientation of its said associated first or second edge (15, 17). opposing top and bottom surfaces; a peripheral side surface extending between the top and bottom surfaces, the peripheral side surface comprising opposing first side surfaces connecting to opposing second side surfaces, each of the first side surfaces and the second side surfaces comprising at least one abutment surface portion (21, 23) suitable for seating the cutting insert; a top peripheral edge formed between the peripheral side surface and the top surface, the top peripheral edge comprising: opposing first edges at the intersection of the first side surfaces with the top surface; opposing second edges at the intersection of the second side surfaces with the top surface, the two opposing first edges extending transversely to the two opposing second edges; a first pair of diagonally opposed first corner edges, each first corner edge defined between a leading end of a first edge and an associated second edge; and a second pair of diagonally opposed second corner edges, each second corner edge defined between a trailing end of the first edge and an adjacent second edge; opposing first edges at the intersection of the first side surfaces with the top surface; opposing second edges at the intersection of the second side surfaces with the top surface, the two opposing first edges extending transversely to the two opposing second edges; a first pair of diagonally opposed first corner edges, each first corner edge defined between a leading end of a first edge and an associated second edge; and a second pair of diagonally opposed second corner edges, each second corner edge defined between a trailing end of the first edge and an adjacent second edge; a symmetry axis extending through the opposing top and bottom surfaces about which the insert has a 180° rotational symmetry; a first axis perpendicular to the symmetry axis and extending generally parallel to the first edges in a top or bottom view of the cutting insert; a second axis perpendicular to both the symmetry axis and to the first axis, the second axis extending along the second side surfaces and being transverse to the first side surfaces; characterised in that in a top view of the cutting insert, relative to an imaginary first edge tangent line A' - A' that is parallel to the first axis and contains a first edge tangent point of the first edge proximate an associated first corner edge, each first edge converges inwardly at a first angle (α) towards the first axis and in a direction of an associated second corner edge; and each of the at least one abutment surface portions (21, 23) is spaced apart from its associated first or second edge (15, 17) and has an orientation which is independent of an orientation of its said associated first or second edge (15, 17).