Britain, who had enjoyed massive profits from drilling operations going back to 1909 and who, by 1950 had come to rely (as did the U.S.) on Middle East oil for 70% of its consumption (even back then). After a hotly contested dispute, which brought in the League of Nations to re-negotiate in 1933, Iran got slightly more of a percentage and by 1946 had negotiated to get 30% profits to Britain's 70%.

After Mossadegh took over and nationalized Iran's oil production, Britain quickly attempted to negotiate a 50/50 split, but Mossadegh would have none of it. The dispute between Britain and Iran went on for two years. So on August 22, 1953, with the help of our very own CIA the Mossadegh government was overthrown and The Shah was reinstated. Shortly after, Britain and Iran were negotiating oil.

And shortly after, The Anglo-Iranian Oil Company became British Petroleum. And the rest, as they say, is history.

This clip comes from a CBS newscast of August 21, 1951 when the negotiations had broken down.