A presidential inauguration with flags instead of people is not merely unique — it is a symbol of both the strength and the fragility of democracy. It is easy to look at the majesty of Wednesday’s swearing in and see the four-yearly transfer of power proceeding smoothly.

But two weeks ago, the Capitol building was under attack from a violent mob determined to overturn the result of a free and fair election. This week, Washington DC has been under what has been, in effect, a police siege, so real was the perceived threat to the inauguration ceremony.

There has been nothing smooth about this transfer from President Trump to President Biden and there has been nothing certain about it, either. The US’s democracy is based on its revered constitution, but even that requires something else: consent. Without that, everything falls apart. And in recent times that consent to abide by the constitution and the rule of law has been challenged.

This is the context in which next week’s Holocaust Memorial Day takes place. Every year it seems to have a different resonance. This year, just a week after the inauguration, we should focus on one of the most basic lessons of the 1930s: the circumstances through which Hitler was able to come to power.

No democracy is safe unless those charged with protecting it honour that role and uphold the rule of law. This is a lesson that the previous US administration seemed to have no interest in remembering. The threats to democracy from the likes of China and Russia are often highlighted. But more insidious is the threat — especially seen in some recently democratic nations — of superficial, sly observance of constitutional rule from leaders who bend and distort the law to cement their positions in power and keep out their opponents.

There will come a time when a line is crossed and the label democracy will no longer apply. The US may have come back from the brink, but this is the danger elsewhere — and it is very real.