BA 893 then BA 640 at Heathrow
Sofia → London → Athens
Timetable, London time
21:50BA 893 from Sofia at the gate
19:45BA 640 to Athens leaves the gate
21 h 55 apart on the timetable, overnight
BA 640 leaves 21 h 55 after BA 893 arrives on the timetable: more than half a day, so not a connection we count.