The biggest single effect is obvious. Oil producers become richer and more powerful. The biggest oil consumers – the US, China and the European Union – become increasingly anxious. Beneath that big trend, there are smaller effects that could change the course of some of the most delicate and dangerous international issues – Iraq, Iran, China's foreign policy and the resurgence of Russia.

The effects of a rising oil price on the economies of the producing countries are dramatic. The Organisation of the Petroleum Exporting Countries made $650bn from oil sales in 2006, compared with $110bn in 1998. Russian oil and gas revenues have quadrupled over the same period.