Gary Locke, the first Chinese-American to serve as US ambassador to Beijing, has had an eventful 28-month tenure, marked by a diplomatic tussle over blind activist Chen Guangcheng and a defection drama that triggered the downfall of Bo Xilai . American ambassadors usually serve about three years in a foreign post. Locke, a third-generation Chinese-American who did not speak English until he was five, took over from Jon Huntsman in August 2011. Huntsman resigned to explore a presidential bid. A photograph of Locke sporting a backpack and ordering coffee with his then six-year-old daughter went viral on the internet and charmed Chinese audiences even before he came to China. Web users often juxtaposed his calm, humble demeanour with the often flashy and lavish photos of local officials. In reality, Locke's ambassadorship was often embroiled in political theatre. In November 2011, Locke visited Chongqing , where he met then municipal party chief Bo Xilai. About three months later, Bo's right-hand man, Wang Lijun , fled to the US consulate in Chengdu , where he recounted a murder story implicating the ambitious politician and offered evidence of corruption in exchange for political asylum. Wang was tried last year and jailed for 15 years; Bo was sentenced to life imprisonment in September. That was the first big test of Sino-US relations during Locke's tenure. In May last year, on the eve of then US secretary of state Hillary Rodham Clinton's visit to meet officials in Beijing, came the case of Chen Guangcheng, a blind activist who sought refuge at the US embassy after escaping from house arrest in Shandong . After intense negotiations between Locke, Assistant Secretary of State Kurt Campbell and Chinese officials, Chen and his family left for the US. This decision, along with a photograph of Locke expressing sympathy to Chen, apparently evoked antipathy from Beijing. The Beijing Daily commented: "What we have seen is not an ambassador to China who is prudent in his words and actions but a standard-issue American politician who goes out of his way to stir up conflict.'' Locke launched an initiative to test and publish figures of PM 2.5 - fine particles causing air pollution. The data released by the embassy became a popular source for determining air quality and shed light on the problem. He was also keen on advancing religious freedom and human rights. The authorities granted him a rare diplomatic visit to Tibet, where he was photographed with Buddhist monks and mixed with locals in Lhasa. Locke plans to step down early next year. It is not yet known who will replace him.