QR 3717 then IB 5408 at Barcelona
Rome → Barcelona → London Gatwick
Timetable, Barcelona time
19:55QR 3717 from Rome at the gatealso IB 5343, LL 5343, VY 6013
13:25IB 5408 to London Gatwick leaves the gatealso LL 5408, VY 7612, BA 8066
17 h 30 apart on the timetable, overnight
IB 5408 leaves 17 h 30 after QR 3717 arrives on the timetable: more than half a day, so not a connection we count.