FB 851 then BA 396 at Heathrow
Sofia → London → Cairo
Timetable, London time
12:10FB 851 from Sofia at the gate
08:55BA 396 to Cairo leaves the gate
20 h 45 apart on the timetable, overnight
BA 396 leaves 20 h 45 after FB 851 arrives on the timetable: more than half a day, so not a connection we count.