What was the british airways flight number from London to anchorage?

BA, BOAC at the time, flew a 707 from London to Japan on Monday, Wednesday and Friday as flight 850. Departed London (LHR) at 1:35PM in the afternoon and arrived in Anchorage (ANC) at 12:45PM the same day. The Tokyo arrival was at 1:15PM one day later. The return trip was flight 851. This information was taken from a 1971 timetable