BA 893 then BA 57 at Heathrow
Sofia → London → Johannesburg
Timetable, London time
22:30BA 893 from Sofia at the gate
21:15BA 57 to Johannesburg leaves the gate
22 h 45 apart on the timetable, overnight
BA 57 leaves 22 h 45 after BA 893 arrives on the timetable: more than half a day, so not a connection we count.