November 5, 2007 deserves to go down in history as a momentous day in the the world’s energy industries: it was when ExxonMobil was displaced as the world’s biggest quoted company by market capitalisation by PetroChina. The thin float and volatility of PetroChina’s shares arguably render the standard calculation of its market value misleading. But the symbolism of the moment still stands: the most admired of all western oil companies is no longer king of the hill.

The transition comes at a time of unprecedented agonising about the future of international oil companies, which is all the more remarkable for coming when the price of oil is close to its all-time high, even in real terms. Past periods of soul-searching inside “Big Oil” have generally coincided with cyclical lows in prices. The trough at the end of the 1990s, for example, prompted the wave of consolidation that joined BP to Amoco and Exxon to Mobil.