PATRONS to the splendiferous Long March Bar at the China Club had better start showing some respect when sitting down in the green and comfy armchairs provided. We can reveal that these chairs have a proud and noble history, having been discovered by the club's top-knob David Tang at Villa 18 in the Diaoyutai State Guest House - the ultra-exclusive complex in Beijing for visiting dignitaries. Set amidst picturesque woods, Villa 18, as it happens, was specially refurbished to accommodate Queen Elizabeth and the Duke of Edinburgh when they last visited China. Exactly what the ubiquitous Mr Tang was doing there is the subject of some inquiries that Keeping Posted has launched in the Chinese capital. (David's explanation - ''I was out on a walk in the woods and there was Villa 18'' - is not entirely plausible.) Anyway, let David carry on: ''The chairs appealed to me the moment I sat down on one. I asked if I could buy them then and there, or at least if they could have some made for me exactly in the same style.'' A few weeks on, and the chairs duly arrived at the China Club where they now offer relaxation - and a certain amount of speculation over the tipples. Says David: ''We're not too sure whether these were the exact chairs used by the Queen or a new set they specially had made for us.'' But then, when we are talking about royal pedigree who wants to quibble about mere details.