A gas turbine engine comprising: forward and aft rotors rotatable about an axis, the aft rotor including: a rotor hub rotatable about an axis and including a bore portion and a rim; and an arm extending axially and radially inwardly from the rim, the arm having a radially inner side and a radially outer side; a row of stator vanes axially between the forward and aft rotors, each of the stator vanes comprising: a platform (80;180) having a first radial side and a second radial side, and a platform axial leading end and a platform axial trailing end; and an airfoil portion extending radially outwardly from the first radial side, the platform axial trailing end including a rear axial face extending from the first radial side and a radially sloped face (192,292;392) extending from the rear face to the second radial side; the gas turbine engine further comprising: a cavity extending from an inlet, between the arm and the platform (80;180) along the second radial side, to an outlet, the inlet being between the row of stator vanes and the aft rotor and the outlet being between the row of stator vanes and the forward rotor, wherein the radially sloped face is substantially flat, and the radially sloped face has an angle, relative to an axis around which the stator vane is situated, of approximately 15° to approximately 60°; characterised in that: the arm includes a protruding ramp on the radially outer side angled in a direction toward the radially sloped face (192;292;392) to direct a stream of air entering the cavity at the inlet toward the platform (88;180). forward and aft rotors rotatable about an axis, the aft rotor including: a rotor hub rotatable about an axis and including a bore portion and a rim; and an arm extending axially and radially inwardly from the rim, the arm having a radially inner side and a radially outer side; a rotor hub rotatable about an axis and including a bore portion and a rim; and an arm extending axially and radially inwardly from the rim, the arm having a radially inner side and a radially outer side; a row of stator vanes axially between the forward and aft rotors, each of the stator vanes comprising: a platform (80;180) having a first radial side and a second radial side, and a platform axial leading end and a platform axial trailing end; and an airfoil portion extending radially outwardly from the first radial side, the platform axial trailing end including a rear axial face extending from the first radial side and a radially sloped face (192,292;392) extending from the rear face to the second radial side; the gas turbine engine further comprising: a cavity extending from an inlet, between the arm and the platform (80;180) along the second radial side, to an outlet, the inlet being between the row of stator vanes and the aft rotor and the outlet being between the row of stator vanes and the forward rotor, wherein the radially sloped face is substantially flat, and the radially sloped face has an angle, relative to an axis around which the stator vane is situated, of approximately 15° to approximately 60°; characterised in that: the arm includes a protruding ramp on the radially outer side angled in a direction toward the radially sloped face (192;292;392) to direct a stream of air entering the cavity at the inlet toward the platform (88;180). a platform (80;180) having a first radial side and a second radial side, and a platform axial leading end and a platform axial trailing end; and an airfoil portion extending radially outwardly from the first radial side, the platform axial trailing end including a rear axial face extending from the first radial side and a radially sloped face (192,292;392) extending from the rear face to the second radial side; the gas turbine engine further comprising: a cavity extending from an inlet, between the arm and the platform (80;180) along the second radial side, to an outlet, the inlet being between the row of stator vanes and the aft rotor and the outlet being between the row of stator vanes and the forward rotor, wherein the radially sloped face is substantially flat, and the radially sloped face has an angle, relative to an axis around which the stator vane is situated, of approximately 15° to approximately 60°; characterised in that: the arm includes a protruding ramp on the radially outer side angled in a direction toward the radially sloped face (192;292;392) to direct a stream of air entering the cavity at the inlet toward the platform (88;180). a cavity extending from an inlet, between the arm and the platform (80;180) along the second radial side, to an outlet, the inlet being between the row of stator vanes and the aft rotor and the outlet being between the row of stator vanes and the forward rotor, wherein the radially sloped face is substantially flat, and the radially sloped face has an angle, relative to an axis around which the stator vane is situated, of approximately 15° to approximately 60°; characterised in that: the arm includes a protruding ramp on the radially outer side angled in a direction toward the radially sloped face (192;292;392) to direct a stream of air entering the cavity at the inlet toward the platform (88;180).