Is this an AONE or an AGLOB? Assuming its the former, you've got a couple of problems. First, you're backtracking by going Asia-Africa-Asia. You have to go Asia-Africa-Europe, meaning you'd need to take a BA flight from CPT-LHR or JNB-LHR (or potentially even NBO-LHR or SEZ-LHR I suppose).

Second, you can't do SYD-PER-BNE. You're only allowed one QF transcon in Australia. Instead do something like SYD-PER-MEL-BNE. PER-MEL isn't counted as a transcon.