A gas turbine engine assembly comprising: a first spool having a first turbine operatively mounted to a first turbine shaft ; a second spool having a second turbine operatively mounted to a second turbine shaft , the first and second turbines mounted for rotation about a common rotational axis (A) within an engine static structure , the first and second turbine shafts coaxial with one another; first and second towershafts respectively coupled to the first and second turbine shafts ; an accessory drive gearbox with a set of gears; a starter generator assembly ; a first clutch disposed between the first towershaft and the starter generator assembly , the first clutch configured to enable the starter generator assembly to drive the first spool through the accessory drive gearbox ; a second clutch disposed between the second towershaft and the starter generator assembly , the second clutch configured to enable the second spool to drive the starter generator assembly through the accessory drive gearbox ; and a transmission coupling the starter generator assembly to the set of gears, the transmission transitionable between a first mode where the starter generator assembly is driven at a first speed relative to the second towershaft , and a second mode where the starter generator assembly is driven at a different, second speed relative to the second towershaft , characterised in that : the gas turbine engine assembly further comprises an oil pump selectively driven by the second towershaft , wherein the starter generator assembly is driven by the second towershaft at a first speed relative to the oil pump when the transmission is in the first mode, and the starter generator assembly is driven by the second towershaft at a different, second speed relative to the oil pump when the transmission is in the second mode. a first spool having a first turbine operatively mounted to a first turbine shaft ; a second spool having a second turbine operatively mounted to a second turbine shaft , the first and second turbines mounted for rotation about a common rotational axis (A) within an engine static structure , the first and second turbine shafts coaxial with one another; first and second towershafts respectively coupled to the first and second turbine shafts ; an accessory drive gearbox with a set of gears; a starter generator assembly ; a first clutch disposed between the first towershaft and the starter generator assembly , the first clutch configured to enable the starter generator assembly to drive the first spool through the accessory drive gearbox ; a second clutch disposed between the second towershaft and the starter generator assembly , the second clutch configured to enable the second spool to drive the starter generator assembly through the accessory drive gearbox ; and a transmission coupling the starter generator assembly to the set of gears, the transmission transitionable between a first mode where the starter generator assembly is driven at a first speed relative to the second towershaft , and a second mode where the starter generator assembly is driven at a different, second speed relative to the second towershaft , characterised in that : the gas turbine engine assembly further comprises an oil pump selectively driven by the second towershaft , wherein the starter generator assembly is driven by the second towershaft at a first speed relative to the oil pump when the transmission is in the first mode, and the starter generator assembly is driven by the second towershaft at a different, second speed relative to the oil pump when the transmission is in the second mode. <EOS>