QR 3717 then BA 483 at Barcelona
Rome → Barcelona → London Heathrow
Timetable, Barcelona time
19:55QR 3717 from Rome at the gatealso IB 5343, LL 5343, VY 6013
15:30BA 483 to London Heathrow leaves the gatealso IB 3780, AY 5938, QR 5984, AA 7061, VY 9561
19 h 35 apart on the timetable, overnight
BA 483 leaves 19 h 35 after QR 3717 arrives on the timetable: more than half a day, so not a connection we count.