FR 4596 then W9 5378 at Barcelona
Porto → Barcelona → London Luton
Timetable, Barcelona time
22:15FR 4596 from Porto at the gate
16:10W9 5378 to London Luton leaves the gate
17 h 55 apart on the timetable, overnight
W9 5378 leaves 17 h 55 after FR 4596 arrives on the timetable: more than half a day, so not a connection we count.