LONDON (Reuters) -The British royals will display their unrivalled soft power when Donald Trump visits Britain next week, seeking to mollify the U.S. President as few others can. Once head of the largest empire in history, the British monarch's main diplomatic job now is to schmooze and dazzle world leaders like Trump at grand state occasions in the hope that they will look upon Britain favourably. "Is there any leader anywhere in the world who has quite that same attraction to Donald Trump as the British monarch?" said historian and author Anthony Seldon.