BA 349 then BA 468 at Heathrow
Nice → London → Madrid
Timetable, London time
21:05BA 349 from Nice at the gate
16:05BA 468 to Madrid leaves the gate
19 h apart on the timetable, overnight
BA 468 leaves 19 h after BA 349 arrives on the timetable: more than half a day, so not a connection we count.