BA 483 then BA 350 at Heathrow
Barcelona → London → Nice
Timetable, London time
19:25BA 483 from Barcelona at the gate
17:00BA 350 to Nice leaves the gate
21 h 35 apart on the timetable, overnight
BA 350 leaves 21 h 35 after BA 483 arrives on the timetable: more than half a day, so not a connection we count.