BA 421 then BA 838 at Heathrow
Luxembourg → London → Dublin
Timetable, London time
19:05BA 421 from Luxembourg at the gate
18:20BA 838 to Dublin leaves the gate
23 h 15 apart on the timetable, overnight
BA 838 leaves 23 h 15 after BA 421 arrives on the timetable: more than half a day, so not a connection we count.