A SUDDEN burst of buying in the closing 30 minutes of trade pulled prices sharply higher on the stock market yesterday, the Hang Seng Index ending the day 46.03 points up. The rise surprised some dealers and analysts. Some said it was due to a sudden burst of optimism on Sino-British relations. Others attributed the rise at least in part to the issue of covered warrants on Cheung Kong by Robert Fleming in London, the first third-party issue for some time. Cheung Kong was one of the best performing shares in the afternoon, and there was speculation more warrants could appear. Cheung Kong ended 1.5 per cent higher at $20.60 on the day's highest turnover of $104.4 million. There were also rumours - since denied by a government spokesman - that Governor Chris Patten had to return to hospital, re-igniting hopes by some investors that he could be forced to step down. ''The performance was unexpectedly strong,'' said Mr Percy Au-young, director of SHK Research. ''It also looks like the market could at least open firm tomorrow. ''It closed near the high so it looks like there may be some follow-through buying, although it depends on whether there are any more attacks [on Mr Patten's democracy proposals].'' The day's trade was still thin, however, with total sales of $1.92 billion. The index closed at 5,835.55, pushed up by utilities, which have under-performed over the past few weeks, and property stocks. The day had a dull start, the index opening slightly lower than Tuesday's close of 5,789.52 and drifting down to the 5,775 level, where it sat until 11.45, touching as low as 5,772.4 at one stage. But a few buyers emerged and met no selling pressure, and prices started to rise, reaching 5,804.19 by the lunch close, 14.67 up. By this time, some dealers suspected a warrant was about to be launched. Buying became more active during the afternoon, the index rising steadily, particularly at the end of the session. During the 30-minute period when futures trade continued and equities were closed, futures contracts continued to rise, indicating buying interest. The February index contract closed at 5,832, up 73 points on the day and within four points of the cash index. However volume fell slightly to 6,020 contracts of all types. Index stocks finding strong demand included World International, which rose 2.8 per cent to $7.45, an increase of 20 cents. Bank of East Asia rose 2.1 per cent to $37, up 75 cents. Hongkong and China Gas rose 30 cents or two per cent to $15.50, and Hongkong Electric was up 30 cents or 1.9 per cent to $16.20. The sub-index with the best performance was utilities, up 1.4 per cent to 7,235.36, a rise of 100.94. Worst was finance, up 9.15 to 5,591.44. Grande Holdings was suspended before trade started and Termbray Industries was suspended before afternoon trade, pending announcements. Guangdong Investment rose 20 cents or 8.7 per cent to $2.50. Earlier this week the company announced projects on the mainland worth $800 million. Innovative International posted a notice during morning trade denying comments made the previous day that it would sell shares to a scientific arm of the China State Council. The statement was unclear on whether such a deal had fallen through overnight, but was clear that no negotiations were now under way. Speculation on which companies would be used as shells by mainland concerns continued. Min Xin Holdings closed up 17.5 cents or 9.2 per cent at $2.075, despite a denial by the company during afternoon trade that a change of control was under negotiation. Similar notices were posted by Keng Fong Sin Kee Construction and CDW International.