Few diplomats have made news like Gary F. Locke. So the news that the US ambassador to China will leave office early next year has attracted widespread media attention, not different from that seen when he was chosen to take up the post two years ago.

Although China's Foreign Ministry has praised Locke's efforts to improve China-US ties, perhaps his least controversial achievement is the reduction in the waiting time for visa for Chinese applicants.

However, the controversies surrounding Locke - from his PM2.5 squabble on air pollution and some Chinese breaking into the US embassy to the US surveillance in Chinese cities - were less because of his working style or personality and more because of the contradictions in China-US relations.