An engine that has, in axial flow series, booster compressor, core compressor, combustion equipment, core turbine, and low-pressure turbine. Core turbine drives core compressor via an interconnecting high-pressure shaft. Low-pressure turbine drives booster compressor via an interconnecting low-pressure shaft. Low-pressure turbine also drives external load having a defined speed characteristic that dictates speed of the low-pressure turbine and booster compressor. Booster compressor has one or more rows of variable stator vanes. The method includes: scheduling variation in the angle of variable stator vanes as a function of speed of the booster compressor wherein the vanes open as booster compressor speed increases; measuring or setting one or more operational parameters which are determinative of temperature at entry to core turbine; and biasing scheduling of angle variation of variable stator vanes as a function of operational parameter(s) to reduce variation in temperature at entry to core turbine.