Defying Cameron, London Mayor Boris to campaign for British EU exit

By William James LONDON (Reuters) - Charismatic London Mayor Boris Johnson was set on Sunday to lend his pulling power to the campaign for a British exit from the European Union, dealing a heavy blow to Prime Minister David Cameron ahead of June's referendum. The decision comes a day after Cameron called the June 23 poll and declared his own intention to campaign for Britain to stay in the EU after clinching concessions from other member states that he said would give Britain a special status in