My memory agrees with finncapt that the SFO B707 routing was eastbound via Tokyo then reverse back to LHR.
DaveReidUK is also correct that the VC10 would not have made LHR-LAX without a tech stop. In fact there was a brief period (1975 or 76 ?) when the VC10s operated LHR-LAX with a scheduled tech stop at Gander. I believe this was because of delays in getting the nonstop DC10 service up and running