By Andy Silvester One of the greater mysteries of the universe is why David Cameron is yet to delete a tweet from the run-up to the 2015 election: “Britain faces a simple and inescapable choice – stability and strong Government with me, or chaos with Ed Miliband.” The voters chose the former, but it is fair to say the country has experienced anything other than stability since that point. There are consequences to that instability – for the UK’s reputation, for one, as well as our appeal as an investment destination. Politics is grown-up business – consistently getting major calls wrong is no …