A rotor stage for a gas turbine engine comprising: a plurality of blades extending from a platform, the blades being formed integrally with the platform, and 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; the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction; the damper element is fixed at a fixing position that is radially inboard of the damper engagement surface; the axial location of the centre of mass of the damper element is different to the axial position of the fixing position such that the damper engagement surface and the platform engagement surface are either urged away from each other or towards each other under the action of centrifugal loading, thereby generating a centrifugal engagement load; characterised in that 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, thereby providing an engagement pre-load, such that an engagement load between the damper engagement surface and the platform engagement surface in use is the sum of the engagement pre-load and the centrifugal engagement load. a plurality of blades extending from a platform, the blades being formed integrally with the platform, and 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; the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction; the damper element is fixed at a fixing position that is radially inboard of the damper engagement surface; the axial location of the centre of mass of the damper element is different to the axial position of the fixing position such that the damper engagement surface and the platform engagement surface are either urged away from each other or towards each other under the action of centrifugal loading, thereby generating a centrifugal engagement load; characterised in that 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, thereby providing an engagement pre-load, such that an engagement load between the damper engagement surface and the platform engagement surface in use is the sum of the engagement pre-load and the centrifugal engagement load. 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; the damper engagement surface and the platform engagement surface are moveable relative to each other in a radial direction; the damper element is fixed at a fixing position that is radially inboard of the damper engagement surface; the axial location of the centre of mass of the damper element is different to the axial position of the fixing position such that the damper engagement surface and the platform engagement surface are either urged away from each other or towards each other under the action of centrifugal loading, thereby generating a centrifugal engagement load; characterised in that 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, thereby providing an engagement pre-load, such that an engagement load between the damper engagement surface and the platform engagement surface in use is the sum of the engagement pre-load and the centrifugal engagement load.