You can imagine the scene in the Oval Office. “Mr President,” says Kurt Campbell, US assistant secretary of state for east Asia. “I thought you should see this dispatch from Kathleen Stephens – you know, our ambassador to Seoul, Sir. She says that a guy named Chun Yung-woo, South Korea’s vice-foreign minister, was speaking to a Chinese official who said that, get this Sir, North Korea has ‘little value to China as a buffer state’.” Mr Campbell pauses to let the significance of the fourth-hand statement sink in.

As far as intelligence goes, this is pretty thin gruel. In fact, it is the very definition of Chinese whispers. This and similar snippets from WikiLeaks are by no means sufficient to conclude, as some have done, that there has been a significant change of heart in Beijing. Suddenly, we are led to believe, China has grown weary of its tantrum-prone North Korean ally and is prepared to prise lips from teeth – Mao Zedong’s favoured metaphor for the tight relationship – even at the cost of the North’s reunification with the South.

Such a conclusion would be hasty indeed. Recent actions by China point to a different conclusion, although it is fair to say that attitudes to Pyongyang have hardened following its two nuclear tests in 2006 and 2009. Yet, significantly, the WikiLeaks cables dry up in February, a month before Pyongyang is thought to have torpedoed a South Korean naval vessel, the Cheonan, with the loss of 46 lives. If there had really been a change of heart, Beijing would surely have condemned that attack. Instead, it refused to accept the conclusions of an international inquiry fingering Pyongyang, and even rewarded Kim Jong-il, North Korea’s leader, with an invitation to China.