FB 851 then MS 784 at Heathrow
Sofia → London → Cairo
Timetable, London time
12:10FB 851 from Sofia at the gate
09:40MS 784 to Cairo leaves the gate
21 h 30 apart on the timetable, overnight
MS 784 leaves 21 h 30 after FB 851 arrives on the timetable: more than half a day, so not a connection we count.