BA 373 then BA 680 at Heathrow
Toulouse → London → Istanbul
Timetable, London time
18:00BA 373 from Toulouse at the gate
17:40BA 680 to Istanbul leaves the gate
23 h 40 apart on the timetable, overnight
BA 680 leaves 23 h 40 after BA 373 arrives on the timetable: more than half a day, so not a connection we count.