BA 825 then BA 1398 at Heathrow
Dublin → London → Belfast City
Timetable, London time
10:30BA 825 from Dublin at the gate
10:05BA 1398 to Belfast City leaves the gate
23 h 35 apart on the timetable, overnight
BA 1398 leaves 23 h 35 after BA 825 arrives on the timetable: more than half a day, so not a connection we count.