Look around the world. What appear to be the biggest potential threats?

Strategists worry about the rise of an authoritarian China, a lawless Russia and the threats of new wars in the Middle East or North Korea. Economists highlight the dangers of a trade war. Lawyers point to the Trump administration's "America First" rejection of international treaties. Environmentalists and a growing number of voters insist on the paramount importance of climate change.

Very few people could argue with a straight face that Germany, or moves toward greater European unity, pose the greatest threat — even to Britain. Yet those views