US President Barack Obama smiles as he talks during a press conference with Britain's Prime Minister David Cameron (R) at the Foreign and Commonwealth Office in central London on April, 22, 2016 following a meeting at Downing Street. 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 / BEN STANSALL (Photo credit should read BEN STANSALL/AFP/Getty Images)
