After four years as the European Union’s top diplomat in Washington, David O’Sullivan will soon leave the US capital – as well as the EU’s civil service. His role as EU ambassador has given him exposure to many of DC’s famous residents, including Barack and Michelle Obama. Photograph: Mandel Ngan/AFP/Getty Images

High on the 10th floor of the EU delegation building overlooking Washington Circle in downtown DC, David O’Sullivan is preparing to leave the office t(...)