Morning departure - Singapore Airlines flight 278 bound for Singapore departing downwind off Rw 23. Duty runway all day before and after this departure had been Rw 05. Obviously the pilot had received permission to use 23 but the tower did seek confirmation as it taxied that 23 was still requested advising a 10 kt tailwind. Due to Covid-19 restrictions traffic was light allowing the flight crew to use the opposing runway on this occasion.