WINDSOR, ENGLAND - APRIL 22: US President Barack Obama, First Lady Michelle Obama and Queen Elizabeth II arrive at the Sovereign's Entrance in the Quadrangle of Windsor Castle driven by Prince Philip, Duke of Edinburgh, after landing by helicopter at Windsor Castle for a private lunch on April 22, 2016. The President and his wife are currently on a brief visit to the UK where they will have lunch with HM Queen Elizabeth II at Windsor Castle and dinner with Prince William and his wife Catherine, Duchess of Cambridge at Kensington Palace. Mr Obama will visit 10 Downing Street on Friday afternoon where he is to hold a joint press conference with British Prime Minister David Cameron and is expected to make his case for the UK to remain inside the European Union. (Photo by Geoff Pugh - WPA Pool/Getty Images)
