Business Secretary Vince Cable has told the government, in a letter leaked to the BBC, that it lacks 'a compelling vision of where the country is heading beyond sorting out the fiscal mess'.The minister also called for 'more leadership' for technologies and for Royal Bank of Scotland to be split up. The damning letter, which was written to Prime Minister David Cameron and Cameron's deputy, Nick Clegg, said: "My suggestion is that we recognise that RBS will not return to the market in its current shape and use its time as ward of state to carve out of it a British business bank with a clean balance sheet and a mandate to expand lending rapidly to sound business."NR