It was created by the British government specifically to serve British interests.
From the official history posted on the BP website:
Churchill was a believer. He thought Britain needed a dedicated oil supply, and he argued the case in Parliament, urging his colleagues to “look out upon the wide expanse of the oil regions of the world!” Only the British-owned Anglo-Persian Oil Company, he said, could protect British interests.
The resolution passed resoundingly, and the UK government became a major shareholder in the company. Churchill had ended Anglo-Persian’s cash crisis, and no one had long to quietly ponder the long-term implications of a company entwining its financial interests with a political entity.
Two weeks later, an assassin killed the Archduke Franz Ferdinand in Sarajevo. Six weeks after that, Germany attacked France. The Great War had begun. By its end, war without oil would be unimaginable.
Despite its name, the British Petroleum brand was originally created by a German firm as a way of marketing its products in Britain. During the war, the British government seized the company’s assets, and the Public Trustee sold them to Anglo-Persian in 1917.
With that, Anglo-Persian had an instant distribution network in the UK, including 520 depots, 535 railway tank wagons, 1,102 road vehicles, four barges and 650 horses.
BTW, according to press accounts, the British government released the Pan Am 103 bomber in exchange for a BP oil deal with Libya--breaking a promise to the US government that he would never be let go. I suggest the US now ask the British to get him back and turn him over to US authorities for trial...
UPDATE: The Wall Street Journal notes BP's Persian connection in today's web post.