For Cameron, a gamble too far

By Mark Trevelyan and William James LONDON (Reuters) - Until last month, the advice David Cameron chose to give fellow British parliamentarians on his last day as prime minister on Wednesday might have seemed apt. "Nothing is really impossible if you put your mind to it," said the man who had rescued his Conservative Party from the political wilderness, won two elections and successfully gambled that Scots would stay in the United Kingdom if given the choice. The June 23 referendum vote for 'Bre