Hong Kong has, for many years, been a gateway to China. For more than two decades, people have made Hong Kong their base for business dealings in southern China and crossed the border regularly and easily. It is a role we are proud of and one that has been enormously beneficial to Hong Kong, to the mainland and to millions of people from western countries.
So what happens when - without any warning or explanation - that gateway is locked or made more difficult to pass through?
That is precisely what has happened in recent weeks with the sudden imposition of severe restrictions on entry into China through Hong Kong.
The potential impact is grave not only for our city and for westerners doing business through Hong Kong but for the mainland as well. And there is little sign yet that either the central government or the Hong Kong government appreciates the long-term damage that is being done.
Since China began opening up in the 1980s, business people based in Hong Kong have visited factories in southern China using multiple-entry visas issued expediently and efficiently and with the minimum of fuss.
For people who do business in Guangdong, those multiple-entry visas are more than just a convenience. They are a necessity upon which, in some cases, the livelihoods of tens of thousands of people depend.
There may be very good reasons for changing visa restrictions temporarily. There may be security issues connected to the forthcoming Olympics or the unrest in Tibet that justify the mainland ceasing to issue multiple-entry visas for a period before things are allowed to return to normal.
If that is the case, however, no one is telling. Instead, we have had the charade of the Ministry of Foreign Affairs responding to concerns voiced by the Hong Kong General Chamber of Commerce by saying there has been no change to China's visa issuing policy or the issuing of multiple-entry visas.
The message in Hong Kong has been just as unhelpful. Here, the Security Bureau has responded to concerns voiced by the Federation of Hong Kong Industries with a letter saying that foreigners are welcome to China and that compared to most other countries, it is relatively easy and convenient to apply for a Chinese visa.
Back in the real world, meanwhile, expatriates who depend on crossing the border up to once or twice a week are being told they can no longer get multiple-entry visas and are having to give up precious time queuing repeatedly for single-entry visas.
Business people from outside Hong Kong, meanwhile, are being told to apply for visas in their home countries rather than in Hong Kong, as well as being asked to supply proof of hotel bookings and return trips out of China.
Through their failure to even acknowledge their difficulties, the mainland and Hong Kong governments risk alienating and driving away these investors. That risk is intensified by the failure to give any indication of when things might return to normal.
Most people understand the need for tightening security from time to time, particularly with the Olympics close by. If these restrictions had been introduced with fair warning and explanation, business people could have prepared, adapted and coped with the situation.
By springing it on travellers without warning or explanation, however, a drama has been turned into what threatens to become a crisis of confidence among foreign investors based in Hong Kong, who are justified in questioning the reliability of the mainland as an investment destination.
China cannot presume too much on its irresistible lure. Already, with high inflation and soaring labour costs, some foreign-invested factories in southern China are being relocated to countries such as Vietnam and Bangladesh.
Denying long-term investors easy access to the factories they have invested in will hardly encourage others to keep their assets in China.
Hong Kong's reputation as a gateway to China, meanwhile, is in ever greater jeopardy the longer this fiasco continues. What use is a gateway, after all, when you have no idea when the gate will be locked or opened so slightly that you can only squeeze through with a huge amount of effort?
The least investors deserve is an explanation from the mainland government. And the absolute least our own government should do is mediate and find out what is going on. Explanations must be sought and delivered with urgency and without further delay.
James Tien Pei-chun is chairman of the Hong Kong Tourism Board and the Liberal Party