Andy Beckett

It's hard to imagine a return to the old relationship with the US

- Thomas Pullin

As wealthy but lightly defended countries have often learned, being close to a much more powerful state - geographically or diplomatically can be a precarious existence. All it takes is an aggressive new government in the stronger state and a relatively equal relationship of economic and military cooperation can suddenly turn exploitative, even threatening.

Since Donald Trump's second inauguration, this realisation has been dawning across the west, but nowhere more disconcertingly than in Canada. Its border with the US is the longest in the world: 8,900km of often empty and hard to defend land, lakes and rivers.

Canada's two biggest cities, Toronto and Montreal, are only a few hours to the north, were you to approach them in a US army tank.

Earlier this month, I spent a week in some of this particularly vulnerable stretch of Ontario and Quebec, encountering a new, more anxious Canada. At times, as the trains I took crawled along the trans-Canadian rail corridor, the roofs of individual American buildings were visible, glinting in the cold sun across the border. The feeling of being a foreigner in a tense, contested place reminded me of when I lived in West Germany, near the East German border, during the early 1980s.

Until Trump started talking so insistently about making Canada his country's "51st state", that would have been an absurd comparison. But not any more.