A method of controlling at least part of a start-up or re-light process of a gas turbine engine, the method comprising: increasing an angular velocity of a low pressure compressor; determining if an exit pressure of the low pressure compressor is equal to or greater than a first threshold pressure; in response to determining that the exit pressure of the low pressure compressor is equal to or greater than the first threshold pressure, controlling rotation of the low pressure compressor using a first electrical machine and controlling rotation of a high pressure compressor using a second electrical machine, to increase angular velocity of the high pressure compressor; determining if an exit pressure of the high pressure compressor is equal to or greater than a second threshold pressure.