All living US ex-presidents – with the notable absence of current White House occupant Donald Trump – joined a star-studded line-up on Thursday for the opening of Barack Obama’s presidential centre in Chicago. Obama, 64, struck his trademark hopeful tone in a speech inaugurating the modernistic centre. The country’s first black president alluded to fears among many Americans that US democracy is in danger, winning applause with the phrase “no kings” – a popular anti-Trump protest slogan. But...