Last week, Xia Baolong gave a foretaste of the political upheavals that will soon shake Hong Kong.

Xia heads the Chinese Bureau for Hong Kong and Macau Affairs and is Beijing's chief official for the special administrative areas in the south of the country.

"Under no circumstances should key positions be occupied by someone who opposes China and disrupts Hong Kong," Xia made clear.

In the future, the principle must apply in Hong Kong: "Patriots rule Hong Kong".

Xia continued: "Not now, not ever."

In a way, Beijing has a Hong Kong trauma.