A variable geometry turbine comprising: a turbine wheel mounted within a housing (101, 403, 901, 903) for rotation about a turbine axis; and an annular inlet passageway (109, 409) extending radially inwards towards the turbine wheel; the annular inlet passageway being defined between a first surface of a radially extending wall (135, 335) of a movable wall member (110, 112, 212, 312, 412, 512, 612, 712, 812) mounted within a cavity (113, 913) provided within the housing and a facing wall (110, 112, 910) of the housing; the movable wall member being movable in an axial direction so as to vary the size of the annular inlet passageway; an array of inlet guide vanes (114, 914) extending across said annular inlet passageway to define a radial vane passage; the radially extending wall of the movable wall member defining a radial second surface that opposes the first surface; the moveable wall member further comprising an annular flange (117, 217, 417) that extends axially into the cavity and which supports a radially extending flange (125, 225, 325, 425) that defines opposing radial third and fourth surfaces (137, 138); the radially extending flange sealing against an annular sleeve provided in the cavity so as to define a first area within the cavity which includes the radial second and third surfaces (136, 137) and a second area within the cavity which includes the radial fourth surface; the first area within the cavity being in fluid communication with a region of the annular inlet passageway upstream of the radial vane passage; and the second area within the cavity being in fluid communication with a region of the annular inlet passageway downstream of the radial vane passage; characterised in that said fluid communication between the second area within the cavity and the region of the annular inlet passageway downstream of the radial vane passage is facilitated by a gas flow path defined between the annular flange and a wall of the cavity by a sealing arrangement (130, 430) between the annular flange and the wall of the cavity. a turbine wheel mounted within a housing (101, 403, 901, 903) for rotation about a turbine axis; and an annular inlet passageway (109, 409) extending radially inwards towards the turbine wheel; the annular inlet passageway being defined between a first surface of a radially extending wall (135, 335) of a movable wall member (110, 112, 212, 312, 412, 512, 612, 712, 812) mounted within a cavity (113, 913) provided within the housing and a facing wall (110, 112, 910) of the housing; the movable wall member being movable in an axial direction so as to vary the size of the annular inlet passageway; an array of inlet guide vanes (114, 914) extending across said annular inlet passageway to define a radial vane passage; the radially extending wall of the movable wall member defining a radial second surface that opposes the first surface; the moveable wall member further comprising an annular flange (117, 217, 417) that extends axially into the cavity and which supports a radially extending flange (125, 225, 325, 425) that defines opposing radial third and fourth surfaces (137, 138); the radially extending flange sealing against an annular sleeve provided in the cavity so as to define a first area within the cavity which includes the radial second and third surfaces (136, 137) and a second area within the cavity which includes the radial fourth surface; the first area within the cavity being in fluid communication with a region of the annular inlet passageway upstream of the radial vane passage; and the second area within the cavity being in fluid communication with a region of the annular inlet passageway downstream of the radial vane passage; characterised in that said fluid communication between the second area within the cavity and the region of the annular inlet passageway downstream of the radial vane passage is facilitated by a gas flow path defined between the annular flange and a wall of the cavity by a sealing arrangement (130, 430) between the annular flange and the wall of the cavity.