The Brexit vote has pummelled the value of the pound to its weakest level against the dollar in more than 31 years and raised the prospect of extreme volatility in other financial markets when they open later today. Confirmation that the UK has voted to leave the European Union has sent sterling down to $1.33, depths it has not been plunged since 1985.  Meanwhile, FTSE 100 Index future derivatives, which give an indication of where the stock market will open at 8am, have slumped 8 per cent.  Some analysts have questioned whether the UK stock market will be able to open on time after volatile trading in Japan overnight, in response to the Brexit vote count, triggered automatic trading circuit breakers on the Nikkei Index. The value of the pound soared as high as $1.50 after polls released after 10pm last night showed a Remain lead. But that mood changed rapidly when the actual count results started to come in, sending it down 11 per cent within hours, the bi...