BA 1401 then BA 680 at Heathrow
Belfast City → London → Istanbul
Timetable, London time
18:25BA 1401 from Belfast City at the gate
18:15BA 680 to Istanbul leaves the gate
23 h 50 apart on the timetable, overnight
BA 680 leaves 23 h 50 after BA 1401 arrives on the timetable: more than half a day, so not a connection we count.