Sterling slides as big backers boost Brexit campaign

By Patrick Graham and Jemima Kelly LONDON (Reuters) - Sterling headed for its biggest one-day fall in David Cameron's six-year premiership on Monday, hit by a rise in the odds of a "Brexit" after London's mayor and other senior ruling Conservatives joined the campaign to leave the EU. Mayor Boris Johnson's announcement on Sunday that he would support an exit from the bloc was seen as giving the "leave" campaign a much-needed figurehead. Sterling hit its weakest level in seven years at $1.4057, w