A gas turbine engine comprising: a compressor section including a lower pressure compressor and a higher pressure compressor , and a turbine section ; a core engine housing surrounding said compressor section and said turbine section ; an outer intermediate housing having a wall defining an internal chamber between said core engine housing and said outer intermediate housing ; and a fan rotor and a fan casing surrounding said fan rotor to define a bypass duct (B) between said fan case and said outer intermediate housing , and a heat exchanger mounted in said internal chamber and configured to receive high pressure air for cooling said high pressure air and configured to deliver said high pressure air into said core engine housing to be utilized as cooling air for a component; wherein said gas turbine engine is configured to utilize air from said lower pressure compressor to cool the higher pressure air in said heat exchanger , a valve controlled by an actuator is configured to be selectively opened and closed to bleed air from said lower pressure compressor , and, when open, said valve is configured to provide air across said heat exchanger for cooling said higher pressure air; characterised in that : the gas turbine engine comprises a control for the actuator programmed to move the valve , wherein said valve is a bleed valve configured to be controlled to lower a load on said compressor section , wherein said valve is configured to be controlled to be partially open at a takeoff condition, wherein said valve is configured to be controlled to be moved towards a closed position, but remain open, at a low power operation wherein power is lower than take off, wherein said lower power operation includes idle operation. a compressor section including a lower pressure compressor and a higher pressure compressor , and a turbine section ; a core engine housing surrounding said compressor section and said turbine section ; an outer intermediate housing having a wall defining an internal chamber between said core engine housing and said outer intermediate housing ; and a fan rotor and a fan casing surrounding said fan rotor to define a bypass duct (B) between said fan case and said outer intermediate housing , and a heat exchanger mounted in said internal chamber and configured to receive high pressure air for cooling said high pressure air and configured to deliver said high pressure air into said core engine housing to be utilized as cooling air for a component; wherein said gas turbine engine is configured to utilize air from said lower pressure compressor to cool the higher pressure air in said heat exchanger , a valve controlled by an actuator is configured to be selectively opened and closed to bleed air from said lower pressure compressor , and, when open, said valve is configured to provide air across said heat exchanger for cooling said higher pressure air; characterised in that : the gas turbine engine comprises a control for the actuator programmed to move the valve , wherein said valve is a bleed valve configured to be controlled to lower a load on said compressor section , wherein said valve is configured to be controlled to be partially open at a takeoff condition, wherein said valve is configured to be controlled to be moved towards a closed position, but remain open, at a low power operation wherein power is lower than take off, wherein said lower power operation includes idle operation. the gas turbine engine comprises a control for the actuator programmed to move the valve , wherein said valve is a bleed valve configured to be controlled to lower a load on said compressor section , wherein said valve is configured to be controlled to be partially open at a takeoff condition, wherein said valve is configured to be controlled to be moved towards a closed position, but remain open, at a low power operation wherein power is lower than take off, wherein said lower power operation includes idle operation. <EOS>