It is almost two months now since the Copenhagen climate change conference, but one incident from the meeting is still causing a buzz in Beijing. It was the moment in one of the tense final sessions when, according to witness accounts, a Chinese official started to jab his finger at Barack Obama, the US president.

More than anything else, that incident has symbolised what many see as a newly aggressive Chinese approach to diplomacy. As a European diplomat said: “If one of the deputy heads of the planning ministry can behave like that to the American president, how are they going to treat the rest of us?”

Almost every day there appears to be a new source of irritation between China and the US about Tibet or Taiwan or the Chinese currency. That is on top of Google, Iran, tyres and chicken feet. And it is not just the Americans: similar stories are being told by Indians, Russians and assorted Europeans.