Just got off QF64 JNB-SYD and we flew way north of the Great Circle Route. So far north that we overflew PER and ADL. The run towards PER was from the WNW direction as far as could be determined from the flight map. Huge tailwinds and got ground speed at 1113 Km/h or so North West of PER. This was a quite a detour over the expected but must have worked out cheaper for fuel burn? We left on time and arrived slightly earlier than scheduled.