US President Donald Trump’s fixation on Greenland offers an ice-cold reminder to leaders in Europe and abroad: no deal is ever final. Trump announced a 10 per cent tariff, rising to 25 per cent in June, on eight European nations, including Denmark, for saying they would undertake token Nato military exercises in Greenland in response to US sabre-rattling. While the tariffs are not certain to take effect, the threat was a brazen escalation and insult to close US allies, trampling over the US-EU...