Next week, Chinese President Xi Jinping, US President Donald Trump and Russian President Vladimir Putin are expected to have a meeting on the sidelines of the Asia-Pacific Economic Co-operation summit in Shenzhen. Two words have been attached to this encounter, which all three governments have confirmed is being discussed: “historic” and “Yalta”. “Historic”, because the three heads of state have never had a formal trilateral before; indeed, it has also been described as “unprecedented”.