BA 893 then VS 449 at Heathrow
Sofia → London → Johannesburg
Timetable, London time
22:30BA 893 from Sofia at the gate
19:15VS 449 to Johannesburg leaves the gate
20 h 45 apart on the timetable, overnight
VS 449 leaves 20 h 45 after BA 893 arrives on the timetable: more than half a day, so not a connection we count.