BA 56 then BA 468 at Heathrow
Johannesburg → London → Madrid
Timetable, London time
04:55BA 56 from Johannesburg at the gate
17:00BA 468 to Madrid leaves the gate
12 h 05 apart on the timetable
BA 468 leaves 12 h 05 after BA 56 arrives on the timetable: more than half a day, so not a connection we count.