CHINA'S official derailment of the through-train will be regarded in many quarters as the inevitable and logical conclusion to its elaborate dialogue of the deaf with Britain. Rather than face international opprobrium for selectively removing its opponents from office, Beijing now believes it is better to be honest from the start and set June 30, 1997 as the end of the legislative term. Seen from north of the border, the through-train is a vehicle for continued British influence, so a new beginning will be better for China and Hong Kong. Yet that logic is flawed. If the post-handover elections were more democratic than the system they replaced, the world would indeed regard it as China's right to start the new era with a new government. But China is now charting a course that assuredly will pit it against international opinion, by imposing a less democratic system on Hong Kong than the one Chris Patten has proposed. At a time when all eyes will be on the territory to see how China handles the transfer of sovereignty, the dismissal of three tiers of government elected under a system seen to be ''open, fair and acceptable to the people of Hong Kong'' will be a public relations disaster. The sad truth is that the announcement was no more inevitable than it was logical. Far from a victory over British intransigence, cancelling the through-train is a missed opportunity for Beijing. It merely saves face where there was much face to be gained. With a little vision, China might have regarded the 1994 and 1995 polls as a challenge. With the resources at its disposal, its experience in United Front work and the quality of some of the leftist politicians ready to fight under the banner of the Democratic Alliance for the Betterment of Hong Kong (DAB), China might have had a good chance of winning. It would have been a democratic and legitimate way of increasing its influence in the territory before 1997. There would have been no need for any threatsof an early takeover. Instead, DAB candidates will be put in the embarrassing position of standing for an election China has disowned. With no pressure to elect candidates likely to ride the through-train, voters may be readier to support the United Democrats in defiance of Beijing. There will be those who argue that if Legco is to be dismissed in 1997 anyway, Mr Patten should abandon all attempts to fit in with the Basic Law and go for full democracy in 1995. But that would have little support from the people of Hong Kong, who havebacked his original plan in opinion polls, but see more radical measures as destabilising. It would also be inconsistent with agreements between Britain and China. Instead, the Governor should now table his original package in the Legislative Council for its quick decision. He has nothing to gain by prolonging the agony until the spring and nothing to lose by championing arrangements that have wide public support.