Barack Obama, outgoing US President has warned of a rise in a crude sort of nationalism following the Brexit and US presidential votes. Speaking in Greece on his final foreign trip, he said we have to guard against tribalism built around an 'us' or a 'them'. He said the US was painfully aware of the danger of divisions along lines of race or religion or ethnicity. <br/><br/>He also put the victory of Donald Trump down to the view of the American people to just shake things up. Mr Obama was speaking after talks with Greek PM Alexis Tsipras in the capital, Athens, as part of a final tour that also takes in Germany and Peru. He said again that he had been surprised by Mr Trump's victory.