A rotor stage for a gas turbine engine comprising: a plurality of blades extending from a platform, the platform extending circumferentially about an axial direction; and a circumferentially extending damper element, wherein: the platform comprises a platform engagement surface that extends in a plane that is substantially perpendicular to the axial direction; the damper element comprises a damper engagement surface that extends in a plane that is parallel to and engages with the platform engagement surface; and the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction, characterized in that: under diametral mode excitation of the rotor stage, the platform is more deformable than the damper element in the radial direction; and the rotor stage further comprises a biasing element (196, 310, 320) that provides a force in the axial direction to the damper element to push the damper engagement surface onto the platform engagement surface, such that the damper element and the platform are axially biased together, thereby providing an engagement load between the damper engagement surface and the platform engagement surface. a plurality of blades extending from a platform, the platform extending circumferentially about an axial direction; and a circumferentially extending damper element, wherein: the platform comprises a platform engagement surface that extends in a plane that is substantially perpendicular to the axial direction; the damper element comprises a damper engagement surface that extends in a plane that is parallel to and engages with the platform engagement surface; and the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction, characterized in that: under diametral mode excitation of the rotor stage, the platform is more deformable than the damper element in the radial direction; and the rotor stage further comprises a biasing element (196, 310, 320) that provides a force in the axial direction to the damper element to push the damper engagement surface onto the platform engagement surface, such that the damper element and the platform are axially biased together, thereby providing an engagement load between the damper engagement surface and the platform engagement surface. the platform comprises a platform engagement surface that extends in a plane that is substantially perpendicular to the axial direction; the damper element comprises a damper engagement surface that extends in a plane that is parallel to and engages with the platform engagement surface; and the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction, characterized in that: under diametral mode excitation of the rotor stage, the platform is more deformable than the damper element in the radial direction; and the rotor stage further comprises a biasing element (196, 310, 320) that provides a force in the axial direction to the damper element to push the damper engagement surface onto the platform engagement surface, such that the damper element and the platform are axially biased together, thereby providing an engagement load between the damper engagement surface and the platform engagement surface. under diametral mode excitation of the rotor stage, the platform is more deformable than the damper element in the radial direction; and the rotor stage further comprises a biasing element (196, 310, 320) that provides a force in the axial direction to the damper element to push the damper engagement surface onto the platform engagement surface, such that the damper element and the platform are axially biased together, thereby providing an engagement load between the damper engagement surface and the platform engagement surface.