Listing the U.S. Presidents chronologically from Washington to Obama, who is the last President that you come to that at some point in his life was a citizen (including duel citizenship) of the United Kingdom and its Colonies (Hint: The correct answer comes much later in the list of U.S. Presidents than most people think.)
Barack Obama (he was a joint citizen from 8-4-1961 to 12-12-1963)