Quite a few factors I've heard regarding the Sydney route, which was almost pulled but BA moved the 77W onto it (Good Cargo Capacity) and better economics than the 747 for that distance. Also it was changed to Mixed Fleet CC.
The BA aircraft appears to sit on the ground in Sydney for around ten hours. That is just about time for a round trip to Wellington, New Zealand. Would the extra leag have a positive or negative effect on the economics of the Sydney route?