FR 6974 then BA 475 at Barcelona
Rome → Barcelona → London Heathrow
Timetable, Barcelona time
16:25FR 6974 from Rome at the gate
11:45BA 475 to London Heathrow leaves the gatealso IB 3658, LA 5488, AA 6814, VY 9553
19 h 20 apart on the timetable, overnight
BA 475 leaves 19 h 20 after FR 6974 arrives on the timetable: more than half a day, so not a connection we count.