THE Chief Secretary, Sir David Ford, is set to become Hongkong's first ''ambassador'' to Europe when he retires from his present post. The current Government plan is for Sir David to step down from the top civil service job in December, although the final decision will hinge on whether the current Sino-British row over the 1995 Legislative Council electoral arrangements can be resolved later this year. If strained Sino-British relations, prompted by the constitutional reform package put forward by Governor Mr Chris Patten, continue to deteriorate, Sir David, who will turn 58 next Monday, is expected to stay longer. Another factor affecting the timing of Sir David's departure will be Mr Patten's health. Mr Patten returns to work today, having undergone heart surgery to widen two arteries. It is understood that Sir David's programme has been planned until November when he will sit in for Mr Patten while the Governor tours France, the Netherlands and Germany. If Sir David, who has held the post of Chief Secretary since 1987, leaves Hongkong at the end of the year, he is likely to succeed Mr John Yaxley as Commissioner of the Government's London Office, and oversee a restructuring of it to become headquarters of Hongkong's overseas offices in Europe. Mr Yaxley is expected to retire in November when he turns 57, the normal retirement age for expatriates. According to current thinking, other government offices in Europe, including those in Brussels and Geneva, will come under the London office, although the title of the commissioner and his office will be changed to reflect expanded functions and role. The plan to group the Government's overseas trade offices is not new as the first step has already been taken in setting up a North America headquarters, which will be headed by the incumbent Secretary for the Civil Service, Mr Barrie Wiggham. He will take up his new post in autumn. Although it is argued that it would be more sensible for the Government to have its European headquarters in Brussels, the constitutional link between Hongkong and Britain before 1997 is said to be a main consideration in choosing London as the base. The headquarters is likely to move to Brussels after 1997. The state of Sino-British relations will not only affect the timing of finding a successor for Sir David, but also the choice, although there is no dispute that the candidate must be a local. Among the three leading contenders are Secretary for Economic Services Mrs Anson Chan Fang On-sang, Secretary for Education and Manpower Mr John Chan Cho-chak and Secretary for Constitutional Affairs Mr Michael Sze Cho-cheung. Although Mr Sze, 47, is considered a rising star, his age and seniority is said to be affecting his chance. While Mr Sze's policy secretary rank has yet to be confirmed, Mrs Chan is already the most senior local officer and Mr Chan a confirmed secretary. Mr Patten is said to need to assess the choice in the light of the on-going row with China. If the current disputes can be resolved and there will be a through-train arrangement for principal officials, the low-key Mr Chan is believed to be the preferredchoice to ensure a seamless transition. However, if the Sino-British tension remains unabated, Mrs Chan, 53, whose tough image in facing China's attack is considered strategically essential, will have an edge over the 49-year-old education and manpower chief. Mrs Chan is considered the preferred transitional figure as she is believed to have no intention of staying beyond the change of sovereignty.