One of the thorniest questions in China is working out the real relationship between state-owned companies and the government.

Ever since the bigger companies started making overseas acquisitions a few years ago, it has also become a diplomatic minefield – notably in 2005 when CNOOC bid for Unocal and set off a political firestorm in the US Congress.

Beijing has been at pains to argue that the big state-owned companies are commercially driven organisations that are forging their own path. And there has been some truth to that explanation – beneath the surface of China's five-year plans and detailed industrial policies, there has always been intense competition between the state-owned groups which sometimes behave like private fiefdoms, duelling for ever-more territory.