LIVEBLOG: Global markets in turmoil

Investment Week and our sister title Investment Europe provide ongoing updates on the turmoil in global markets as investors fret over the US and European debt crises.

15.45 Rumour has it that ratings agency S&P will downgrade the US after markets shut this evening. According to the Financial Times, Barclays said: "To be honest it would not come as a complete surprise as S&P always said that chance of a cut is 50:50. They also said they wanted the US government to cut expenditures by at least 4 trn; they have now cut it just shy of more than 2trn. "So to be consistent and not loose their credibility S&P actually needs to cut the ratings". Separately and unsurprisingly, Bloomberg reports Merkel and Sarkozy's planned phone call will also take place followin...