BA 1453 then BA 43 at Heathrow
Edinburgh → London → Cape Town
Timetable, London time
18:55BA 1453 from Edinburgh at the gate
18:25BA 43 to Cape Town leaves the gate
23 h 30 apart on the timetable, overnight
BA 43 leaves 23 h 30 after BA 1453 arrives on the timetable: more than half a day, so not a connection we count.