BA 513 then BA 874 at Heathrow
Lisbon → London → Bucharest
Timetable, London time
10:05BA 513 from Lisbon at the gate
09:50BA 874 to Bucharest leaves the gate
23 h 45 apart on the timetable, overnight
BA 874 leaves 23 h 45 after BA 513 arrives on the timetable: more than half a day, so not a connection we count.