Britain's Queen Elizabeth II (3rd R) and her husband Prince Philip, Duke of Edinburgh (4th R) speak with US President Barack Obama (2nd R) and his wife Michelle (R) after they landed by helicopter outside Windsor Castle, west of London, on April 22, 2016. US President Barack Obama plunged into Britain's increasingly poisonous EU debate on Friday at the start of a visit, warning strongly against Brexit and pointing out that US soldiers had died for Europe. / AFP / Jim Watson (Photo credit should read JIM WATSON/AFP/Getty Images)
