A turbine comprising: a turbine housing, a wastegate passage connecting the turbine inlet and the turbine outlet; and a wastegate valve comprising a movable valve member. The wastegate valve has an open state in which a first gas may pass between a turbine inlet a turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents said first gas from passing between the turbine inlet and the turbine outlet. The valve member is mounted to an actuation member that passes through a bore of the turbine housing. The actuation member is movable to move the wastegate valve between the open and closed states. The turbine comprises a fluid conduit configured to deliver a second gas to the bore to form a fluidic seal between the bore and the actuation member to substantially prevent the passage of said first gas along the bore.