LONDON (Reuters) - New British Foreign Secretary David Miliband, seeking to squash speculation that London may distance itself from Washington over Iraq, has insisted the U.S. is still Britain's number one ally. Since Gordon Brown took over from Tony Blair as British prime minister last month, he has been at pains to stress there is no cooling off in Anglo-American relations -- but two of his ministers offered mixed signals. Development Secretary Douglas Alexander said in a speech in Washington that while Britain stood beside the United States in fighting terrorism, isolationism did not work in an interdependent world. Then...