When oil traded at $122 a barrel in early 2008, the commodities team at Goldman Sachs predicted that West Texas Intermediate oil was “likely” to rise to between $150 and $200 a barrel over the next two years. Oil promptly fell to $40 a barrel later that year.

Three years on, as political and social unrest in the Middle East and North Africa pushes up oil prices again, the predictions for $200 a barrel are back on. Last Friday, former Saudi oil minister Sheikh Zaki Yamani said oil could even reach $300 if civil unrest engulfs his country.