The shadow of history hovers over Iran at the moment.
And it is not just the student protests 30 years ago, which helped bring down the Shah and which launched the 1979 Iranian Islamic Revolution, that are worth recalling.
Also relevant is what happened 20 years ago. 1989 was the start of the transformation of the Soviet Bloc, symbolised above all by the fall of Berlin Wall at the end of 1989, which paved the way for the abrupt collapse of the entire Soviet Union two years later, and the end of the Cold War.
And that upheaval tangentially helped inspire another collapse: the end of the apartheid regime in South Africa, another seemingly unexpected revolution that brought a fresh breeze of hope to world politics.