BA 475 then BA 868 at Heathrow
Barcelona → London → Budapest
Timetable, London time
13:10BA 475 from Barcelona at the gate
13:00BA 868 to Budapest leaves the gate
23 h 50 apart on the timetable, overnight
BA 868 leaves 23 h 50 after BA 475 arrives on the timetable: more than half a day, so not a connection we count.