“Follow the money” is the advice routinely offered to detectives in low-budget thrillers. For anyone attempting to understand the ebbs and flows of international politics, I offer a variant of that old line: “Follow the oil”.

Any suggestion that the search for energy is fundamental to the foreign policy of Britain and the US is often treated as faintly indecent. In Britain, the government is currently angrily brushing off suggestions that the decision to release Abdelbaset Ali Mohmed al-Megrahi, the Libyan convicted of the Lockerbie bombing, had anything to do with Libya's oil and gas. Jack Straw, the UK justice secretary, has released letters in which he spoke of considering prisoner transfers to Libya, in the context of “wider negotiations” and the “overwhelming interests” of the UK. He did not use the word “oil”; but, under mounting pressure, he has since admitted that trade and oil interests were “a very big part” of Britain's desire to bring Libya “back into the fold”.

It is true that oil is not the only interest Britain has at stake in Libya. But the search for more secure and diverse energy supplies is increasingly important to UK foreign policy. Britain's North Sea reserves are running down and the country is worrying about a looming energy crisis. Libya looks like a promising possible supplier of both oil and natural gas that is unusually open to foreign oil companies. BP and Royal Dutch Shell are the second and third biggest companies on the London stock exchange, and they have both signed exploration deals in Libya.