Firing the opening salvos of a trade war, Donald Trump said his reasons were simple: stop “illegal aliens” and put an end to the flow of fentanyl, a deadly opioid, on to America’s streets.

Prime Minister Justin Trudeau set out "far-reaching" tariffs of 25%, affecting 155bn Canadian dollars' worth ($106.6bn; £86bn) of American goods ranging from beer and wine, to household appliances and sporting goods.