On the day before moving into Number 10, David Cameron told his wife he wouldn't be PM – such was the uncertainty in the negotiations to form a coalition government following this year's General Election. Cameron also reveals that when he went to Buckingham Palace to see HM The Queen he told her he didn't know what sort of government he would form and that he might have to return in the morning. The BBC's political editor, Nick Robinson, tells the inside story of the forming of the coalition government, in Five Days That Changed Britain.