Britain has sold a 2.1 billion pound ($3.3 billion) stake in Royal Bank of Scotland (RBS) (RBS.L) to kick off the disposal of its holding seven years after bailing out the bank, sparking a political row that the sale at a loss was being hurried. Finance Minister George Osborne on Tuesday hailed the start of returning RBS to the private sector and said it was right to commence selling at a loss to the price paid in the 2008 rescue.