The grasp that ordinary Chinese people have on western politics can be humbling. During the British general election in May, one taxi driver regaled me with his lengthy version of the Gordon Brown-Gillian Duffy incident; last month, another inquired what I thought of Harold Macmillan.

Only a handful of politicians become household names around the world. Margaret Thatcher was one, Tony Blair another; he still features regularly in the Chinese media.

So far, David Cameron has yet to make that kind of impact. In our small and entirely unscientific sample in central Beijing, not one person could name the British prime minister.

Some cited Blair. One thought, after a minute of umming, that it might be Brown.

When we mentioned Cameron, a news-stand owner said he had heard of him, but that he had not made much of an impression. Then there was the passer-by who confused him with director James Cameron, perhaps on the grounds of their shared affection for blue people.

No doubt Cameron's name will be more readily recognised by the time he leaves for South Korea on Thursday.

But one young woman was proof that it can take years to establish yourself. Asked to identify the current prime minister, she paused for a second before venturing hopefully: "Churchill?"