In November 2017, a year after he first won the US presidency, Donald Trump was given a lesson on trade by Malcolm Turnbull. At least, that’s how it appeared.

Four months earlier, in July, Turnbull and then-finance minister Mathias Cormann, on the sidelines of the G20 summit in Hamburg, had gone to work on Trump, his treasury secretary at the time, Steve Mnuchin, and the then commerce secretary, Wilbur Ross, about plans to impose tariffs and quotas on Australian steel and aluminium.