BA 349 then BA 680 at Heathrow
Nice → London → Istanbul
Timetable, London time
21:05BA 349 from Nice at the gate
17:40BA 680 to Istanbul leaves the gate
20 h 35 apart on the timetable, overnight
BA 680 leaves 20 h 35 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.