BA 349 then BA 934 at Heathrow
Nice → London → Düsseldorf
Timetable, London time
21:05BA 349 from Nice at the gate
12:45BA 934 to Düsseldorf leaves the gate
15 h 40 apart on the timetable, overnight
BA 934 leaves 15 h 40 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.