For those in doubt of China's generosity towards Hong Kong, here are some statistics.

As of the end of last year, 95 per cent of live pigs, 100 per cent of live cattle, 33 per cent of live chicken, 100 per cent of freshwater fish, 90 per cent of vegetables and 70 per cent of flour consumed by Hong Kongers were supplied by the mainland.

And then there were those long bleak days in 2003, when the Sars epidemic struck, fear settled over the city and Beijing "promptly lent a helping hand", providing free medical supplies even as Chinese leaders visited hospitals to console victims.

The details are among many painstakingly laid out in a White Paper - the first ever on the one country, two systems framework that has governed China's relationship with Hong Kong in the past 17 years - heralding the model a "widely recognised success".

Released last week by China's Cabinet, or the State Council, the document is 14,500 words long, was issued in seven languages and is sold for a song - HK$5 (S$0.80) - at bookshops here.

Behind the niceties though, the real message is far more pointed: Beijing is in total control of Hong Kong - high degree of autonomy or not - and will not hesitate to intervene in its affairs, whether by doling out benefits or cracking the whip.

The "two systems" in the equation, the document states, are subordinate to "one country".

Hong Kong's autonomy "is not an inherent power but one that comes solely from the authorisation by the central leadership".

And so, whatever autonomy Hong Kong enjoys is at Beijing's pleasure. What it gives, it can also take back.

Another key point concerns the long-promised system of universal suffrage for selecting the chief executive and legislative council (LegCo) - the form of which is now under contentious debate.

The White Paper ups the ante by invoking the issue that "the country's sovereignty, security and development interests" are at stake. The chief executive "must be a person who loves the country and Hong Kong" - taken to mean the ruling out of anyone from the pan-democracy camp.

Judges, categorised as among Hong Kong's "administrators", also need to fulfil this "basic political requirement".

While similar sentiments have been articulated before by Beijing officials, they have never been quite so baldly and formally stated. Not surprisingly, there have been accusations here that Beijing is backtracking on its pledges.

The Sino-British Joint Declaration of 1984, which formed the basis for Hong Kong's mini-constitution, the Basic Law, promised that its system and liberties would remain unchanged for 50 years after the 1997 handover.

Hong Kong would be ruled by Hong Kongers, with "a high degree of autonomy", except in foreign and defence affairs.

In those nervy, delicate times, Hong Kongers accepted with relief these terms for a return to Chinese rule.

Few cared to peer too hard at how they would be defined and executed. A deliberate vagueness served all sides well.

Now, less than halfway into the 50 years, Beijing clearly believes it is time to state its bottom line far more forcefully - a move that will exact a certain price.

The fractured pan-democracy camp in Hong Kong could unite in anger over the issue of constitutional reform.

A public referendum on the issue is being organised starting this Friday, while a protest march will take place on July 1.

Also, the original target for which the one country, two systems policy was devised - Taiwan - will look askance at these developments.

An already unattractive model for unification with mainland China looks even more so now.

However, Beijing appears to have calculated that there is greater upside to the move.

One reason is its alarm over what it perceives to be an increasingly chaotic Hong Kong society that is perverting the "correct" way of how the one country, two systems model should work.

In recent years, the city has been roiled by conflict, with the government often unable to garner support for its policies. Most right-thinking analyses attribute this to the current dysfunctional model that allows the people to elect the LegCo but not the chief executive.

This leaves the latter flailing without a popular mandate.

Beijing clearly sees it differently. The problem, says the White Paper, is that some are "confused or lopsided in their understanding of one country, two systems and the Basic Law".

The pan-democrat lawmakers are accused of stymying the city's Beijing-anointed leader. A vibrant anti-establishment civil society and the Occupy Central movement threatening civil disobedience for what it calls "genuine democracy" are deemed subversive. Those from the pro-independence fringe raise yet more hackles.

Here, to Beijing's mind, would be grounds for intervention. The late Chinese leader Deng Xiaoping is quoted in Deng Xiaoping Wenxuan, a compendium of his philosophy, as saying: "The central government will not hurt Hong Kong's interests, and we hope Hong Kong will not hurt the national interests and its own. But what if it does? We have to intervene."

Clearly, the point has been reached where the central government believes developments in Hong Kong could be detrimental to itself and the nation's interests.

Second, the White Paper is likely to be a pre-emptive move by Beijing to absolve itself of any blame should the fraught process of constitutional reform not work out. Failure will lie with the intransigent who "did not properly understand" the Basic Law.

Third, some observers see the fingerprints of President Xi Jinping, whose instincts appear more politically conservative than those of his predecessors, in this more hardline approach.

Moreover, challenges in both the domestic and international environments are driving the desire to clamp down on recalcitrant Hong Kong.

So what will change with this White Paper?

In Hong Kong, the space for autonomy will shrink. Political scientist Peter Cheung expects that the chief executive will be increasingly dictated to by Beijing.

Also, across the sea, Taiwan is watching developments carefully. Activists there already view the White Paper as a warning that there will be no longer be a permissive model of one country, two systems for the island.

But with any possibility of a cross-strait reconciliation far off in the future, Beijing's calculation appears to be that it would be safer to tighten its grip around the bird in its hand first.

xueying@sph.com.sg