THE real reason for maverick pro-China lawyer Liu Yiu-chu's threat to quit the working panel for the Preparatory Committee days before last week's inaugural meeting in Beijing have become clear. Ms Liu, who seems to be making walk-outs a habit these days, is less than enamoured of fellow-member Sir S. Y. Chung, the former Executive Council member. To be frank, she cannot stand the sight of him according to what she told P.S. last week, and resents the fact he was invited to join the working panel. She walked out of a Hongkong advisers meeting with Hongkong and Macau Affairs Office deputy director Wang Qiren after 10 minutes because she refused to be in the same room as Sir S. Y. The roots of antipathy are unclear, although Ms Liu clearly has strong doubts about the depth of his commitment to the future Special Administrative Region (SAR). ''I don't want to have a picture with him [Sir S. Y.]; I am clean but he is dirty. We are working on the future of the SAR government; I don't know whether they will leak our secret to the British,'' she said. Ms Liu, practically hauled from a stage in May after making equally forthright comments about Governor Chris Patten, during the Hongkong Journalists' Association annual dinner, continued in the same vein about Sir S. Y. for some time, although the libel laws preclude us from including them here.