AS Sir Robin McLaren is driven through the secluded grounds of the Diaoyutai State Guesthouse towards Villa No 10 this morning, the normally poker-faced ambassador might allow himself a slight smile. The Foreign Office mandarin will not fail to notice the symbolic significance of the spring-like setting for perhaps the most crucial negotiations of his 35-year career in the diplomatic service. The lilacs and peonies will be in full bloom, while the peach trees and weeping willows lining the lakes will provide an additional splash of colour to the picturesque gardens. The scene will stand in stark contrast to the gloomy atmosphere during the Governor Mr Chris Patten's visit to Beijing last October when cold autumnal winds blew through Diaoyutai covering the lakes and villas in blanket of dead leaves. Sir Robin could well be hoping that the spring, being the traditional season of renewal, will breath new life into Sino-British negotiations on the future of Hongkong, stalled throughout the long cold winter that set in after the Governor's ill-fated visit. The ambassador will at least be assured of a courteous and friendly - if not exactly rapturous - welcome from his Chinese counterpart, Vice-Foreign Minister, Mr Jiang Enzhu. Sir Robin is very much the acceptable face of the British negotiating team. He is considered by Beijing to be an ''old friend of China'' and his disagreements with the Governor on the pace of democratisation in Hongkong are well documented. The ambassador's more tactful and cautious approach to relations with Beijing have clearly been appreciated by the Chinese authorities and as the Governor himself has acknowledged it was the ''eloquence'' of his ''good friend'' Sir Robin that largely contributed to the reconvening of talks. If there is anyone on the British side Vice-Minister Jiang feels he can do business with, then Sir Robin is probably the man. However it should be stressed that at times Mr Jiang has been just as rude and unpleasant to Sir Robin as the left-wing newspapers have been about Mr Patten, but then Sir Robin can provide some strategically-placed insults of his own as well. Diplomats in Beijing say that while the two men could not be described as friends, they at least understand each other. ''There is a far greater chance there will be a meeting of minds this time,'' one European diplomat said, referring to the Governor's comment on his first day of face to face talks with the head of China's Hongkong and Macau Affairs Office, Mr Lu Ping, last October. Once the two teams sit down for talks, Mr Jiang is likely to focus his attention almost exclusively on Sir Robin and try to isolate the ''advisers'' from Hongkong, which he and his colleagues from Mr Lu Ping's office evidently consider to be unwelcome guests. Neither is Mr Jiang expected to call on his ''advisers'' unless it is absolutely necessary, so as to avoid setting a precedent for group discussions. The scene outside the negotiating room will be very different however. Once the talks have closed for the day, the British team will return to the embassy to conduct a post-mortem on the day's events, dispatch memos to Whitehall and Government House and discuss tactics for the following day. The team will meet again the next morning before talks resume to discuss last-minute changes or overnight instructions from London. It is during these brainstorming sessions that the other members of the team and the embassy's support staff will come into their own. Secretary for Constitutional Affairs Mr Michael Sze Cho-cheung and the Political Adviser Mr William Ehrman will be responsible for drafting replies to points raised by Mr Jiang although the ambassador will amend the draft as he feels necessary. Mr Sze's deputy Mr Peter Lai Hing-ling will bring his expertise on constitutional matters to the debate while Mr Peter Ricketts, head of the Foreign Office's Hongkong Department, will provide the ''London angle'', relaying the concerns of the Cabinet andParliament. The basic negotiating strategy, or steering brief, for what are expected to be three days of talks was finalised in Hongkong this week after being outlined in London during the Easter break. Insiders say the Governor played a very active role in drafting the steering brief and that if the Chinese side think they can force an agreement that Mr Patten would not approve they are very much mistaken. The embassy brainstorming sessions are essentially exercises in fine-tuning and tend to be very democratic and open, insiders say. ''The ambassador is not an autocrat and listens to everyone's point of view,'' one British official said. Others doubt that Sir Robin is really a good team-player. While he is very competent and professional, on a personal level Sir Robin is not always an easy man to get on with, colleagues say. The ambassador is extremely fastidious and a stickler for detail, a quality which will probably prove invaluable if Britain is to hammer out a watertight agreement with China but which has on occasion led to considerable annoyance and frustration among his staff. A former officer at the embassy recalled how Sir Robin had amended a draft memo which mentioned General Secretary Jiang Zemin to read ''General Secretary of the Chinese Communist Party, Mr Jiang Zemin''. ''What did he think I meant, General Secretary of the Transport and General Workers Union?'' asked the exasperated diplomat. Meanwhile back at Diaoyutai, the Chinese team will also be in a huddle but these sessions will probably be rather less democratic. Although Mr Jiang has been nominated to lead talks for the Chinese side, there can be no doubt that it is Mr Lu Ping who will be directing operations from behind the scenes. Mr Jiang will report the day's events directly to Mr Lu and while other members of the team such as the head of the Hongkong and Macau Affairs Office, Mr Wang Fengchao, the head of the Foreign Ministry's Hongkong Office, Mr Zhao Jihua, will be called upon for their opinions it is Mr Lu who will decide the strategy for the next session. Reports on the day's negotiations will be forwarded to the State Council but the Chinese team will be working to such a tight brief that it is unlikely there would be any major deviations from the plan which would require the intervention of higher authorities. Analysts say Mr Lu will largely be left to run his own show.