"Chinalco’s acquisition of a 12pc stake in Rio Tinto helped push the miner down 73p to close at £55.27 as some traders took the view that a Chinese blocking stake could mean that suitor BHP Billiton will not be able to get hold of its target or that it may even abort its bid altogether."
http://www.telegraph.co.uk/money/main.jhtml?xml=/money/2008/02/05/cxmktrep104.xml