BA 349 then BA 834 at Heathrow
Nice → London → Dublin
Timetable, London time
21:05BA 349 from Nice at the gate
15:25BA 834 to Dublin leaves the gate
18 h 20 apart on the timetable, overnight
BA 834 leaves 18 h 20 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.