FR 553 then FR 340 at Dublin
Manchester → Dublin → London Luton
Timetable, Dublin time
21:25FR 553 from Manchester at the gate
12:50FR 340 to London Luton leaves the gate
15 h 25 apart on the timetable, overnight
FR 340 leaves 15 h 25 after FR 553 arrives on the timetable: more than half a day, so not a connection we count.