It is no more a surprise that US President Donald Trump is seldom removed from controversy. But even by the most generous yardstick, his recent swing through Europe must count as an epochally newsmaking period. He successively attacked the North Atlantic Treaty Organisation, kept Queen Elizabeth II waiting at a ceremony, criticised British Prime Minister Theresa May's Brexit strategy and finished his tour with a summit meeting in Helsinki with Russian President Vladimir Putin where he seemed to lay trust in Mr Putin's denials over the considered view of America's intelligence community that Moscow did interfere in the last US presidential election.

As always, there are kernels of truth in even some of the most egregious remarks from America's 45th president. Nato is a Cold War-era construct that was boosted into a military alliance after the Korean War. Nato's continued expansion - the latest, Montenegro, joined during the Trump presidency - may have sharpened Russian insecurities. It is reasonable to expect Europe to pick up more of the tab for its collective defence as Mr Trump has demanded. He has railed against tariffs imposed by some of his allies, quite understandably. But his proposed manner of fixing this risks seriously damaging a global trading system the US helped to create and nurture, and benefited from too.