A gas turbine engine rotor comprising: a body having a solid-of-revolution-shaped portion centered around a rotation axis (24; 124), wherein the body includes a hub disposed at a radially inner end of the body and circumscribing a bore extending axially through the body, the bore being adapted to receive a shaft therein; an annular cavity defined by the body and centered around the rotation axis (24; 124), the annular cavity extending between two opposite annular wall portions (33, 35) each leading to a corresponding edge of an annular opening; and a plurality of structural plates (40; 140) disposed circumferentially around the rotation axis (24; 124) and mounted to and extending axially between the two opposite annular wall portions (33, 35), wherein the annular cavity penetrates into the body from the annular opening and radially outwardly into the body from the axial bore, wherein each one of the two opposite annular wall portions (33, 35) corresponds to a face of a corresponding one of a forward annular flange portion of the hub and a rearward annular flange portion of the hub, each of the forward annular flange portion and the rearward annular flange portion being located at an opposite axial end of the annular cavity, and each of the structural plates (40; 140) forms an interference fit with the two opposite annular wall portions (33, 35), characterised in that: radially inwardly opening apertures are provided and are configured to provide fluid flow communication to and from the cavity across the plurality of structural plates (40; 140), wherein the plurality of structural plates (40; 140) are provided with the apertures across a radial thickness thereof, or wherein the structural plates (40; 140) are circumferentially interspaced from one another by corresponding spacings and the apertures are provided by the corresponding spacings left between circumferential edges of the structural plates (40; 140); and the annular cavity is enclosed on all sides except for the radially inwardly opening apertures. a body having a solid-of-revolution-shaped portion centered around a rotation axis (24; 124), wherein the body includes a hub disposed at a radially inner end of the body and circumscribing a bore extending axially through the body, the bore being adapted to receive a shaft therein; an annular cavity defined by the body and centered around the rotation axis (24; 124), the annular cavity extending between two opposite annular wall portions (33, 35) each leading to a corresponding edge of an annular opening; and a plurality of structural plates (40; 140) disposed circumferentially around the rotation axis (24; 124) and mounted to and extending axially between the two opposite annular wall portions (33, 35), wherein the annular cavity penetrates into the body from the annular opening and radially outwardly into the body from the axial bore, wherein each one of the two opposite annular wall portions (33, 35) corresponds to a face of a corresponding one of a forward annular flange portion of the hub and a rearward annular flange portion of the hub, each of the forward annular flange portion and the rearward annular flange portion being located at an opposite axial end of the annular cavity, and each of the structural plates (40; 140) forms an interference fit with the two opposite annular wall portions (33, 35), characterised in that: radially inwardly opening apertures are provided and are configured to provide fluid flow communication to and from the cavity across the plurality of structural plates (40; 140), wherein the plurality of structural plates (40; 140) are provided with the apertures across a radial thickness thereof, or wherein the structural plates (40; 140) are circumferentially interspaced from one another by corresponding spacings and the apertures are provided by the corresponding spacings left between circumferential edges of the structural plates (40; 140); and the annular cavity is enclosed on all sides except for the radially inwardly opening apertures. radially inwardly opening apertures are provided and are configured to provide fluid flow communication to and from the cavity across the plurality of structural plates (40; 140), wherein the plurality of structural plates (40; 140) are provided with the apertures across a radial thickness thereof, or wherein the structural plates (40; 140) are circumferentially interspaced from one another by corresponding spacings and the apertures are provided by the corresponding spacings left between circumferential edges of the structural plates (40; 140); and the annular cavity is enclosed on all sides except for the radially inwardly opening apertures.