The Trial of Christine Keeler, the BBC television series that started on Sunday evening, provides a fresh interpretation of the Sixties Profumo affair, which convulsed the establishment and came to define an era.
The reason we keep returning to the Swinging Sixties is that it was the point of change from which everything then followed.
Some see it as a welcome sloughing off of archaic constraints in favour of individual empowerment. Others view it as a loss of moral and cultural compass. Regardless, this upending of the old order had its roots in the aftermath of the Nazi Holocaust.
That event delivered a seismic shock from which the West has never recovered. It took place in Germany, the crucible of European modernity and high culture. It thus delivered a body blow to the West’s idea of itself as the home of reason and civilised values.
There has been, in short, a retreat from reason. Only if this is understood can we make sense of the antisemitism now sweeping the West.
The signature characteristic of antisemitism is that it is deranged. A culture that allows it to roar out of control is therefore invariably a culture in deep trouble.
So on the eve of 2020, how will the coming decade be defined? It could be, as Boris Johnson promises, the start of a golden age for Britain in which divisions are healed and the nation bonds again in a shared commitment to national values of decency and rationality.
Or it could be the equivalent of the Weimar Republic a century ago: the brittle and decadent precursor of a terrible showdown between those who defend western civilisation and those who want its building blocks destroyed.
We know all about the Swinging Sixties; we are about to discover which way the Twenties will swing.
To read my whole Times column (£), please click here.