FR 635 then FR 340 at Dublin
Cardiff → Dublin → London Luton
Timetable, Dublin time
17:05FR 635 from Cardiff at the gate
14:40FR 340 to London Luton leaves the gate
21 h 35 apart on the timetable, overnight
FR 340 leaves 21 h 35 after FR 635 arrives on the timetable: more than half a day, so not a connection we count.