Georgina Godwin speaks to Robert Zoellick, a man whose experience in the US government spans six presidencies. Having served in a number of roles such as deputy secretary, counsellor of the State Department and as US trade representative, his illustrious career also includes stints as deputy chief of staff at the White House and president of the World Bank. Now a senior fellow at Harvard University, his latest book is ‘America in the World: A History of US Diplomacy and Foreign Policy’.