BA 349 then IB 720 at Heathrow
Nice → London → Madrid
Timetable, London time
21:05BA 349 from Nice at the gate
17:25IB 720 to Madrid leaves the gate
20 h 20 apart on the timetable, overnight
IB 720 leaves 20 h 20 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.