OVER the past week, coverage of the long-awaited Sino-British negotiations has focused on an issue many thought was resolved: the so-called through train. Like the expressions ''second stove'' and ''three-legged stool'', the novelty of the through train metaphor wore off long ago. It is nonetheless important because it concerns whether elected members of the Legislative Council will be permitted to continue to serve in the first legislature of the Special Administrative Region. In fact, the rationale of the current round of Sino-British talks is to ensure that the legislature formed in 1995 will continue, under a different sovereign, until 1999. And if it was not thought necessary for the legislature to continue, why should there be talks at all? The debate about the through train is really about the train's destination. Is it to be democratic or undemocratic? Put another way, is it the Hongkong voters - or Beijing's veto - that will decide who will serve in the first Hongkong Special Administrative Region? The point of democratic elections is that Hongkong people should choose their own representatives, not Beijing's. Many in the press have suggested that the Chinese negotiators have a trump card: the threat to derail the through train. The impression is that Hongkong is doomed without the through train, and thus the British Government must reach an agreement - any agreement - so that China will allow a through train. But when we pause to examine the facts, it is evident that the through train arrangement is in reality much more vital to China. The reason is the rather obvious point that the British responsibility to Hongkong ends on June 30, 1997. From then on, Chinaalone must cope with setting up an SAR government capable of maintaining stability and prosperity. In theory, the first SAR government will be formed on July 1, 1997. In practice, it would be impossible to do so without some workable framework. In the Government, for instance, China must be able to identify key senior civil servants and fill these positions with qualified individuals. However one looks at it, China needs British co-operation - before and after 1997. China's promise was not to take over Hongkong and make it part of its communist system, but rather to keep it distinct and functioning. The likelihood of an embarrassing inability to run Hongkong's vast bureaucracy means that it would be far better - from China's perspective - for Hongkong to have in place a government and legislature before 1997 that would continue after the British administration has ceased. With the legislature, it is more difficult, because the Joint Declaration requires the SAR legislature to be fully constituted by elections. In theory, of course, elections can be held on July 1, 1997, but that would by no means be a smooth transition, and might even be a humiliating failure (Headline: ''Hongkong's New Communist Rulers Hold an Election and No one Shows up to Vote''). It would be infinitely better if that legislature were formed before 1997 on the understanding that it would continue beyond the transfer of sovereignty. This rationale seemed to be the crux of the secret correspondence between the British and Chinese Governments on the 1995 Legislative Council elections in Hongkong in early 1990. Mr Douglas Hurd and Mr Qian Qichen exchanged seven letters that in effect legitimised China's pre-1997 controlling role in 1995 in order to secure the through train. This was later embodied in the Basic Law and the decision made by the NPC at the same time the Basic Law was promulgated on April 4, 1990. The NPC set the through train out in these terms: ''. . . Members of the last Hongkong Legislative Council who uphold the Basic Law of the Hongkong SAR of the People's Republic of China and pledge allegiance to the Hongkong SAR of the People's Republic of China, and who meet the requirements set forth in the Basic Law of the Region, may, upon confirmation by the Preparatory Committee, become members of the first Legislative Council of the Region.'' In simpler terms, if Britain wants the legislature elected in 1995 to go beyond 1997, these requirements must be met - the alternative is no through train. THIS casts no duty whatsoever on Britain to comply with these requirements. It merely gives them the option to comply with the Basic Law, even though it does not take effect until July 1, 1997. Britain has thus far chosen to adhere to the Basic Law. (Governor Patten's reform proposals were severely limited because of this.) Through relentless intimidation and inflexibility, Beijing has managed to twist the option of the through train to be viewed as a hard and fast commitment to converge with the Basic Law. And to make the through train possible, China has demanded that no electoral reform take place without its authorisation. Thus when Mr Patten failed to give China a veto on his reforms before he presented them, China broke out the Cultural Revolution dictionary to describe him. Beijing also declared his proposals, now in the form of a Bill, to be contrary to ''the Joint Declaration, the Basic Law and the relevant understandings''. So even if it is not mentioned as part of the negotiations, the Chinese case is built on the foundation of the through train. China's leadership has insisted that the Governor should withdraw or abandon his proposals during the current negotiations. No doubt they would, in due course, force Britain to accept Chinese proposals for 1994-95 elections - something they are not entitled to do under the Joint Declaration and Basic Law. But without the through train, all Chinese leverage at the negotiating table evaporates. As these talks run their course, Britain must be prepared to walk away from the concept of the through train. If there is no through train, it is absolutely not the case that all bets are off - that the Basic Law and Joint Declaration are null and void. It merely means that in 1997, China will do what it likes with our local government. There is a strong case that China will do that anyway. There are various possibilities about the destination of the through train. The best case would be that in the course of negotiations, the two sovereigns agree that they owe the people of Hongkong a measure of certainty about their future and declare that anyone who stands for election and is fairly elected may serve through the change in sovereignty. Hongkong would then have democratic and accountable government both before and after 1997. Of course, the alternative is that there is no agreement on the through train and July 1, 1997, Beijing will dissolve Legco, kick out those representatives chosen by the people of Hongkong and insist on its own hand-picked team. But should the negotiations yield no agreement on the through train, there is also the possibility that China will let the Government continue - and we will have in effect a through train. Once the train is on the right track rolling towards 1997, it is my firm belief that China will let it go through, intact. Beijing will not derail a legislative arrangement that is good for the people of Hongkong. Those who assume that China will deliberately destroy a structure that is fair and reflects the wishes of the people of Hongkong take a dim view of the PRC indeed.After the British Administration has gone, and the people of Hongkong have expressed their wishes through the ballot box, Beijing should see no reason to dismantle a perfectly workable Legco. Moreover, thanks to Hongkong's rule of law, there are some significant legal considerations that bolster my confidence that China ultimately will not derail democracy in Hongkong. As I have noted, the Basic Law obliges any individual who wants to serve in the SAR legislature so pledge allegiance to the Special Administrative Region, agree to uphold the Basic Law and meet the requirements set forth in the Basic Law. Anyone can feel comfortable in complying with these conditions. Occasionally, there have been totally unreasonable interpretations of these provisions. All too frequently it is insinuated that swearing allegiance to the Special Administrative Region is the same thing as pledging allegiance to the SAR Government. Swearing allegiance to the government is the equivalent of saying: ''I will not oppose government policies.'' I would refuse to swear allegiance to the Hongkong Government today, nor will I swear allegiance to the SAR Government tomorrow. Furthermore, the most senior members of China's leadership have stated without reservation that China will uphold the Joint Declaration and the Basic Law, although there is a serious inconsistency between the Chinese leaders' regular promises to respect these documents and their periodic threats to remove members of Legco who do not tow the Beijing line. Implicit in all of this is that there is no veto over legislators given to Beijing. In the course of negotiations, there may be the temptation to exclude one or two legislators to placate China, but the British Government must resist this if it is to have any legitimacy as a sovereign before 1997. Most people assume that the dispute over the through train only centres around a couple of people: my United Democrats colleague Mr Szeto Wah and myself. But if today we are told that two people - even if they are elected in 1995 and conform to all requirements of the Basic Law - will be thrown off the through train, then tomorrow, there will be four people. And when we come to 1997, there will be 20, or 40 unacceptable people. But that is not really all either. As long as Beijing can veto a single legislator, then all 60 may find it necessary to tow the Beijing line on all sensitive issues and even consult Beijing's representative in Hongkong, the NCNA, on how to vote. China could engender much goodwill in Hongkong by saying that it will not tolerate the expulsion of any individual Legco member for exercising his or her fundamental rights that are guaranteed under the Joint Declaration and the Basic Law. To settle onceand for all the uncertainty surrounding the question of the through train, Beijing should state now, in no uncertain terms, that legislators are not to be barred from holding public office for expressing their political beliefs. Martin Lee Chu-ming is chairman of the United Democrats of Hongkong and a democratically-elected Legislative Councillor.