EC 1703 then IB 723 at Madrid
Nice → Madrid → London Heathrow
Timetable, Madrid time
20:40EC 1703 from Nice at the gate
16:45IB 723 to London Heathrow leaves the gatealso LA 1702, VY 5421, QR 6907, AA 8770
20 h 05 apart on the timetable, overnight
IB 723 leaves 20 h 05 after EC 1703 arrives on the timetable: more than half a day, so not a connection we count.