Brexit campaigner Boris Johnson could be next PM - Cameron

By Kylie MacLellan ISE-SHIMA, Japan (Reuters) - Former London mayor Boris Johnson could be Britain's next prime minister despite heading the campaign to leave the European Union, Prime Minister David Cameron said. Last year, Cameron, who has said he will not stand for a third term at a national election due in 2020, cited Johnson, along with Home Secretary Theresa May and Chancellor George Osborne, as potential successors. Cameron and Johnson now find themselves rivals on opposing sides of an in