FR 6921 then U2 2326 at Barcelona
Dublin → Barcelona → London Luton
Timetable, Barcelona time
21:40FR 6921 from Dublin at the gate
10:20U2 2326 to London Luton leaves the gate
12 h 40 apart on the timetable, overnight
U2 2326 leaves 12 h 40 after FR 6921 arrives on the timetable: more than half a day, so not a connection we count.