In March 2006 Zhang Zhiru, founder of the Shenzhen Migrant Workers Association, collected 10,000 signatures requesting free arbitration services for workers in labour disputes. For his trouble, police in the southern Chinese manufacturing hub detained the activist for four hours.

A few months later, Mr Zhang organised an online drive that generated a similarly strong response. “The two petitions were quite successful,” he says. “But as a result, our association was banned by the government.”