The olive branch offered by the Democrats to Beijing two months ago was partly motivated by a desire to strike the right note with voters in the Legislative Council election. And the positive response by both mainland and Hong Kong officials might also be attributed to a desire to calm the political climate ahead of the poll. But the welcome peace initiative was always going to be tested during the hotly contested election campaign. And this has proved to be the case. The farcical on-off trip by leading Democrat Law Chi-kwong to the mainland is the latest in a series of controversies involving the Democratic Party. Democrats have resisted the temptation to lump the incident with their other allegations of a mainland-inspired smear campaign. This is to their credit. But at a time when rumour, suspicion and conspiracy theories abound, it is important that the questions raised by the affair are answered. Dr Law, a member of the party's executive committee and leader of its election campaign, was due to join an academic delegation to Shanghai and Beijing at the weekend. His attendance would have been something of a breakthrough in the party's relations with the central government. Dr Law would have been the highest ranking party member allowed to visit the mainland in recent years. He claims he was given approval by the central government's liaison office in Hong Kong, and publicised the good news ahead of his trip. But on arrival in Shanghai on Saturday, he was refused entry. He said he was told by immigration officers that his presence on the mainland was 'against the interests of the country'. Dr Law's home-return permit was confiscated and he was put on a plane back to Hong Kong. It is not yet clear how the confusion over Dr Law's status arose. The liaison office said it was unclear about what happened. Its deputy director said yesterday he had no knowledge of the approval that Dr Law said he was given by his office. The trip had been organised in association with the liaison office. It normally checks the list of delegates to ensure that all are permitted to enter the mainland. Liaison office officials have also been at the forefront of moves to improve ties with the pro-democracy camp. In the case of Dr Law, something went wrong. There appears to have been a breakdown in communication. It may have been that Dr Law mistakenly thought he had been given the go-ahead to attend. Or perhaps the liaison office had a different understanding to that of officials on the mainland. Either way, the matter should be clarified, so that the public understands the situation. As the September 12 election approaches, these matters take on a greater significance than would normally be the case. The bigger issue, however, is the fact that Dr Law was refused entry at all. His presence on the mainland was surely harmless. He was due to attend an academic conference and there were no plans for him to meet officials responsible for Hong Kong. Allowing him to enter would have been a positive step forward in the long and difficult process of building trust between the Democrats and Beijing. Dr Law was apparently told that he 'should know better' why he was being denied entry. But the vague assertion by an immigration officer does little to help our understanding of the position. Since the party sought to improve its ties with Beijing, senior mainland officials have cautiously welcomed a thawing of relations. Some high-profile members of the pro-democracy camp have been allowed to visit the mainland. The refusal to let Dr Law cross the border does not help this process. But after 15 years of hostility, it will take a long time for a relationship based on trust to emerge. The weekend's events should not be allowed to hinder efforts on both sides.