The Tokyo, Honolulu, San Francisco, London routing had ceased by the time of the merger between BEA and BOAC in 1974.
Not quite, but not far off. The VC10 LHR-JFK-LAX-HNL-NAN-SYD operated for one year after the merger and was replaced by the Air New Zealand DC10 interchange LHR-LAX-HNL-NAN-AKL from Summer 1975. SFO wasn't on the BA/BOAC network at the time, came along a few years later.