To outsiders, who assume that China is a closed and controlled society, this might sound like a small change. But to the liberal intellectuals and online chattering classes who have long enjoyed the freedom to argue, at least among themselves, this marks a sinister step-change. "Western capitals are failing to understand the magnitude of what is happening now," says Nicholas Bequelin, of Human Rights Watch in Hong Kong. "The Chinese authorities are actively seeking to try to redefine the boundaries of which opinions are tolerable, and which are not."