Donald Trump and Xi Jinping face off in Germany this weekend at the most pivotal Group of 20 meeting since the 2008 global financial crisis when world leaders joined forces to pump trillions of dollars of stimulus to resuscitate the slumping global economy.

The summit's agenda has been hijacked by angry words over North Korea's belligerent first test this week of an intercontinental ballistic missile that has the potential to hit the US mainland, and within a couple of years could have a nuclear warhead attached.