IB 721 then BA 680 at Heathrow
Madrid → London → Istanbul
Timetable, London time
17:15IB 721 from Madrid at the gate
17:10BA 680 to Istanbul leaves the gate
23 h 55 apart on the timetable, overnight
BA 680 leaves 23 h 55 after IB 721 arrives on the timetable: more than half a day, so not a connection we count.