An airfoil for a gas turbine engine comprising: an outer airfoil wall providing an exterior surface and multiple radially extending cooling passages (92,94,96,98;196,198), the exterior surface providing pressure and suctions sides (86,88) joined by leading and trailing edges (82,84), the cooling passages including a supply passage (96;196) for a trailing edge cooling passage (98; 198), the supply passage (96; 196) being arranged upstream from in fluid communication with the trailing edge cooling passage (98;198), a cooling hole (124;224) extending through the outer airfoil wall from the supply passage (96;196) to the exterior surface on the suction side, wherein the cooling passages include first, second and third cooling passages (92,94,96;196) provided by first and second walls (100, 102) that extend internally between the outer airfoil wall and progressively aftward of one another, the supply passage provided by the third cooling passage (96;196), and wherein the first cooling passage includes a first baffle and the second cooling passage includes a second baffle, the first and second baffles (104,106) including multiple cooling holes to provide impingement cooling on inner surfaces of the cooling passages (92,94,96;196), the cooling hole being arranged downstream from the second baffle; and wherein the first baffle is spaced apart from the inner surface of the first cooling passage by a first rib, the second baffle is spaced apart from the inner surface of the second cooling passage by the second wall and a second rib, the third cooling passage (96;196) includes third ribs, and the first, second and third ribs (108, 110, 112) are spaced apart from one another in a radial direction, permitting fluid flow in a chordwise direction; characterised in that: the radially extending first, second, third and trailing edge cooling passages (92,94,96,98;196,198) are fluidly connected to one another in the chordwise direction. an outer airfoil wall providing an exterior surface and multiple radially extending cooling passages (92,94,96,98;196,198), the exterior surface providing pressure and suctions sides (86,88) joined by leading and trailing edges (82,84), the cooling passages including a supply passage (96;196) for a trailing edge cooling passage (98; 198), the supply passage (96; 196) being arranged upstream from in fluid communication with the trailing edge cooling passage (98;198), a cooling hole (124;224) extending through the outer airfoil wall from the supply passage (96;196) to the exterior surface on the suction side, wherein the cooling passages include first, second and third cooling passages (92,94,96;196) provided by first and second walls (100, 102) that extend internally between the outer airfoil wall and progressively aftward of one another, the supply passage provided by the third cooling passage (96;196), and wherein the first cooling passage includes a first baffle and the second cooling passage includes a second baffle, the first and second baffles (104,106) including multiple cooling holes to provide impingement cooling on inner surfaces of the cooling passages (92,94,96;196), the cooling hole being arranged downstream from the second baffle; and wherein the first baffle is spaced apart from the inner surface of the first cooling passage by a first rib, the second baffle is spaced apart from the inner surface of the second cooling passage by the second wall and a second rib, the third cooling passage (96;196) includes third ribs, and the first, second and third ribs (108, 110, 112) are spaced apart from one another in a radial direction, permitting fluid flow in a chordwise direction; characterised in that: the radially extending first, second, third and trailing edge cooling passages (92,94,96,98;196,198) are fluidly connected to one another in the chordwise direction.