SIR Robin McLaren will have a worthy opponent in Mr Jiang Enzhu, according to Western diplomats. ''He is a very competent negotiator, has a good grasp of the issues and has a straightforward, no-nonsense approach to doing business,'' one diplomat said. ''He is also very courteous and relaxed. No matter how difficult talks become, he will never raise his voice or get into an argument.'' Promoted to vice ministerial rank in 1991, Mr Jiang is an expert on European and North American affairs, but, despite a stint in the Chinese embassy in London 15 years ago, his expertise on Hongkong is believed to be limited. Many observers believe this lack of experience will to be Britain's advantage, not because the British team will have more information - Mr Jiang will have been well briefed beforehand - but because he is not part of the hardline school of ''Hongkong experts'' who would be more likely to stonewall talks. Mr Jiang ''can be very creative in negotiations and will not just stick to the party line but it should be stressed he will never deviate from the brief he has been given'', a European diplomat said. Before his 1991 promotion, Mr Jiang was sent to the Central Communist Party School in Beijing for an intensive three-month course, designed essentially to recharge his ideological batteries. The course helped reinforce his commitment to party ideology, observers say, but did not transform him into a party hack. ''He now has a much stronger grasp of ideological matters but is still someone who deals in facts, real issues and is not one to act like a self-righteous guardian of the faith,'' the European diplomat said. Given his background and temperament, observers say the talks are likely to hinge on just how flexible or narrow a brief he is given. ''If he is given a flexible brief then things could get interesting but I personally think that is unlikely,'' a political analyst said. ''The Chinese like to work to tight briefs and take things one day at a time. That is the advantage they have of being in Beijing. ''They can regroup at the end of the session and discuss tactics for the next day, something which will not be so easy for the British.'' Due to China's insistence that the talks be a bilateral affair between Britain and China, Hongkong and Macau Affairs Office chief Mr Lu Ping could not very well take part in the negotiations. But there is no doubt he will be directing operations from behind the scenes. How much freedom Mr Lu has in determining the bottom line for the negotiations is less certain but most signs indicate he will be granted a fair degree of autonomy.