BA 349 then BA 1368 at Heathrow
Nice → London → Manchester
Timetable, London time
21:05BA 349 from Nice at the gate
12:55BA 1368 to Manchester leaves the gate
15 h 50 apart on the timetable, overnight
BA 1368 leaves 15 h 50 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.