Asian shares tumble after Japan's S&P downgrade

S&P cut Japan's long-term sovereign debt rating to AA minus for the first time since 2002, saying Tokyo lacked a plan to deal with its economic problems. The main Nikkei index closed down 118.32 points, or 1.1%, at 10,360.34, but was still up 0.8% for the week. It comes as the International Monetary Fund has told Japan, America, Brazil and many other indebted countries  they must implement deficit cutting plans, or risk a repeat of the sovereign debt crisis that has engulfed Greece and Ireland. London's index of 100 leading shares opened down 0.58%, or 34.45 points, to 5,930.63...