The significance of yesterday's announcement about trimming the size of the frontier closed area lies not only in how much land will be opened up for development but also what parts of it will remain closed. As expected, the area will shrink from 2,800 to 800 hectares, as there is no longer a need to cordon off a large swathe of land to deter illegal immigration. Officials have given assurances that planners will pay due regard to protecting the sensitive ecology of the 2,000 hectares to be opened for possible development. That is heartening. But what really deserves our attention most are the decisions to continue to seal off the Lok Ma Chau loop - a 96 hectare plot of land created by a realignment of the Shenzhen River - and Shataukok's Chung Ying Street, which is bisected by the line of demarcation between Hong Kong and Shenzhen. The decisions are noteworthy as they amount to saying an emphatic 'no' to any proposals to undermine the integrity of our border with the mainland. Considering the backgrounds of the proponents of these proposals, the administration should be commended for sticking to its principled position. Since before the handover, industrialists have argued that the Lok Ma Chau site should be turned into an industrial zone. Its most prominent backer was none other than Henry Tang Ying-yen, who was chairman of the Federation of Industries before joining the cabinet of first chief executive Tung Chee-hwa as secretary for commerce, industry and technology. He has since become financial secretary. Mr Tang proposed developing a cross-border zone where thousands of would-be immigrants would be housed on the Shenzhen side and industry and commerce on the Hong Kong side. He felt the zone would not only help alleviate the potential influx of mainland spouses and children of Hong Kong permanent residents but also help Hong Kong industries regain their competitive edge. While Mr Tang has not publicly championed the idea since joining the government, it has never dropped off the agenda of the industrial lobby. In 2004, legislator Sophie Leung Lau Yau-fun, who represents the textiles and garment sector, proposed a motion calling for the construction of an industrial zone at Lok Ma Chau. The motion was carried with support from the Liberal Party, Democratic Party and the then Democratic Alliance for the Betterment of Hong Kong. This was despite official reservations about the high cost of cleaning up the heavily contaminated site and putting in the needed infrastructure. In 2000, Cheng Yiu-tong, an executive councillor and a member of the Commission on Strategic Development, proposed building a shopping complex on the Hong Kong side of Chung Ying Street to cater for the large numbers of mainland visitors drawn there because of its novelty value. His proposal was not adopted by the government. Yesterday's announcement has affirmed a continual need to restrict access to the street on security grounds. It is to be hoped that the decisions to maintain the status quo of Lok Ma Chau loop and Chung Ying Street would put an end to any further attempts to tamper with the border. Lest anyone should forget, the Basic Law provides that Hong Kong remains a separate customs territory, for both people and goods, until 2047. While steps should be made to facilitate the flow of people and goods across a more porous border, it cannot be dispensed with. Apart from satisfying strict environmental safeguards, any future developments in the newly opened-up area should not invite suspicions that the border will cease to exist. The idea of exploiting the best of both worlds by building factories and housing that straddle the border is a dangerous one, although the government has refrained from saying that explicitly. Once we start to fudge the border, we would risk undermining local and international confidence in the foundations of 'one country, two systems'.