Originally Posted by
Darkmarkster
Ah excellent, so the booking itself would be placed as two separate bookings,one with BA to JNB and the second directly with SAA to Gabarone, will that still be ok to check all the way through from Heathrow?
No.
You should book one ticket, typically with BA as the first carrier, connecting to BA. Booking is irrelevant. All that matters is the ticket and it will have two segments. That is the entire purpose of an interline ticketing agreement. You may find that you need to book this by phone although start online to see what turns up.