In 1980 BA were still doing a weekly 747 operation Hong Kong to Johannesburg, as Cathay hadn't got into long haul ops by then. How was that crewed ? A triangle LHR-HKG-JNB-LHR ?
I flew the 747C for BA in the mid to late 80s and the above flight was still being operated, twice a week as I remember. The full routing was LHR-ANC-NRT-HKG-CMB-SEZ-JNB and vv. It was flown by a 741 and held the record as the longest air route in the world at that time.
The crews were rostered for parts of the trip, to/from NRT was part of the daily operation there and the NRT-HKG sectors were flown by crews that had arrived or departed from/for LHR Similarly the sectors between HKG and CMB were flown as part of a triangular trip and so too was the CMB-SEZ-JNB. The latter was not much sought after as it was a 2 sector night flight with the "interesting" round the bay visual circling approach at SEZ in the monsoon at certain times of the year.