However, what we do know is what we can see precisely because it was on open display, a display designed and rightly recognised as a timely reminder of the power relationships in the special administrative region where autonomy has been granted but control has hardly been relinquished.

It has been pointed out that Mr Xi's modest warning to Mr Tsang is infinitely less damaging than the dressing down given to his hapless predecessor Tung Chee-hwa by President Hu Jintao which effectively signalled the end of his reign, but this is to miss the point. What Mr Xi was doing was to remind Mr Tsang, and everyone in Hong Kong, who is in charge.

This public way of reinforcing control is entirely typical of authoritarian, patronage-led systems that offer a modicum of autonomy but do so within strictly controlled limits. I vividly recall covering the Singapore election when the patriarch Lee Kuan Yew stood down and handed the premiership to his chosen successor Goh Chok Tong. At an election rally with Mr Goh sitting by his side, Mr Lee delivered a speech outlining his successor's inadequacies, particularly in the area of public speaking but patronisingly declared that the new boy would learn. His real message, of course, was that while Mr Goh might be allowed to occupy the prime minister's office, he only did so because Mr Lee was gracious enough to allow it and the old man would remain in charge.

Mr Tsang's situation is not very different. He sits in the chief executive's office because the authorities in Beijing have selected him to be there. As in Singapore, they allow the farce of an election to install the new leader but in reality the election means little because the mandate of heaven can easily be withdrawn and will not, as in the case of Mr Tung, require an election to facilitate the process. The situation would be very different if Hong Kong's chief executive had a popular mandate and even more different if a genuine system of universal suffrage was responsible for installing a government. This does not mean that elected officials would face less criticism - indeed, they would probably face more - but they could fight back and would not need to be publicly humiliated by their bosses.

Mr Tsang is a strong supporter of this authoritarian system, and he and his officials are working night and day to devise a way of seemingly honouring the pledge to allow genuine elections while seeking ways of undermining an elective system thus ensuring that patronage and control from above will prevail.

Therefore any sympathy for Mr Tsang must be tempered by the knowledge that his humiliation is caused by the system he earnestly wishes to preserve. Perhaps he knows or suspects that if a democratic system were in place things would be even worse for him. As his administration blunders into yet further areas of public discontent, if a genuine election were to be held there would be little chance of Mr Tsang being chief executive and most, if not all, of his ministers would be relegated to the fate of being no more than ordinary citizens.

Stephen Vines is a Hong Kong-based journalist and entrepreneur