A cooling system for a gas turbine engine, the cooling system comprising: a first plenum bounded in part by a first portion of an engine casing and a mounting hook; the first portion of the engine casing disposed radially outward from a rotor stage adjacent to a stator vane; the mounting hook connecting the stator vane to the engine casing between the first portion of the engine casing and a second portion of the engine casing disposed radially outward from the stator vane; a first cooling flow passageway in fluid communication with the first plenum and with a first airfoil cooling channel within an airfoil of the stator vane; the first airfoil cooling channel for cooling a leading edge of the airfoil; the first cooling flow passageway disposed within the mounting hook; and a second cooling flow passageway in fluid communication with the first plenum and with a platform cooling channel within an outer diameter platform of the stator vane; the second cooling flow passageway disposed within the mounting hook; wherein the first cooling flow passageway and the second cooling flow passageway are not in fluid communication with each other; characterised in that the cooling system further comprises: a second plenum bounded in part by the second portion of the engine casing and the mounting hook; and a third cooling flow passageway disposed within the outer diameter platform of the stator vane in fluid communication with the second plenum and with a second airfoil cooling channel within an airfoil of the stator vane to cool the trailing edge. a first plenum bounded in part by a first portion of an engine casing and a mounting hook; the first portion of the engine casing disposed radially outward from a rotor stage adjacent to a stator vane; the mounting hook connecting the stator vane to the engine casing between the first portion of the engine casing and a second portion of the engine casing disposed radially outward from the stator vane; a first cooling flow passageway in fluid communication with the first plenum and with a first airfoil cooling channel within an airfoil of the stator vane; the first airfoil cooling channel for cooling a leading edge of the airfoil; the first cooling flow passageway disposed within the mounting hook; and a second cooling flow passageway in fluid communication with the first plenum and with a platform cooling channel within an outer diameter platform of the stator vane; the second cooling flow passageway disposed within the mounting hook; wherein the first cooling flow passageway and the second cooling flow passageway are not in fluid communication with each other; characterised in that the cooling system further comprises: a second plenum bounded in part by the second portion of the engine casing and the mounting hook; and a third cooling flow passageway disposed within the outer diameter platform of the stator vane in fluid communication with the second plenum and with a second airfoil cooling channel within an airfoil of the stator vane to cool the trailing edge. a second plenum bounded in part by the second portion of the engine casing and the mounting hook; and a third cooling flow passageway disposed within the outer diameter platform of the stator vane in fluid communication with the second plenum and with a second airfoil cooling channel within an airfoil of the stator vane to cool the trailing edge.