BA 349 then BA 640 at Heathrow
Nice → London → Athens
Timetable, London time
21:05BA 349 from Nice at the gate
19:45BA 640 to Athens leaves the gate
22 h 40 apart on the timetable, overnight
BA 640 leaves 22 h 40 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.