Mark Carney stood before a walnut-veneered lectern, his face drawn tight, as he announced that talks with Canada’s biggest trading partner had collapsed. “Last spring, I warned that America is trying to break us so that they can own us,” he said. “And I promised: that will never, ever happen. We are keeping that promise.”

For years, the former central bank governor had worked hard to calm markets. Now, he was asking Canadians to accept uncertainty and confrontation.