BA 349 then BA 506 at Heathrow
Nice → London → Lisbon
Timetable, London time
21:05BA 349 from Nice at the gate
11:55BA 506 to Lisbon leaves the gate
14 h 50 apart on the timetable, overnight
BA 506 leaves 14 h 50 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.