Sometimes migration is a matter of fashion - lots of Americans flooded to the Paris of the 1920s for example.

In the early 2000s, something similar happened on a smaller scale with British citizens who had an affinity with Germany, often because they’d studied the language at university.

Once again you have a sense of how migration is shaped by a combination of large global factors and small personal decisions.

In many parts of the EU, the precise scale of those trends has become hard to measure because movement between member states - in the theology of European integration - wasn’t seen as migration in the traditional sense. That is the essence of the policy of Freedom of Movement.

But if key chapters in history, like the shared Hanoverian monarchy and the British military presence, shaped migratory flows in the past, then it’s reasonable to assume that Brexit will provide another, similar moment of change.

The official estimate of the number of UK citizens living in Germany is a pleasingly precise 116,470. There is even a symmetry in the way that the number of Germans living in the UK roughly matches the number of British migrants who’ve travelled in the opposite direction - just over 100,000 in each case.

The actual number may be slightly higher or lower because it’s not clear exactly how individuals with dual nationality are counted. Germany allows people to hold joint citizenship with another country as long as it’s an EU member state. That’s included the UK until now but may not after Brexit.

For that reason the number of British applications for dual nationality or naturalisation has jumped as Brexit looms - from 622 in 2015 to 7,493 in 2017, and what’s anticipated to be a higher number for the next 12-month period to be measured.

Source: Destatis (Federal Statistical Office of Germany)

The effect of Brexit so far has been to create a mood of anxiety among British expatriates in other EU member states.

There is uncertainty over how access to state healthcare will be managed in the future and over long-term issues such as arrangements for paying pensions in one country, when they are based on National Insurance contributions in another.

Some will have to consider applying for a passport from another member state to protect their status as EU citizens, even if that means giving up British nationality, as it probably will in Germany.

Similar factors weigh on the three million or more EU citizens who’ve made their home in the UK.

In a field notoriously hard to measure and predict, it seems safe to say that migration between countries like Germany and the UK will continue, even if the legal and political framework around migration changes.

That’s because a small minority of people have always been ready to leave their homes and move between countries, and the reasons are often subtle and not likely to be swayed by the prevailing political climate. Often people are driven by a sense of adventure, by job opportunities created through language skills or simply because they fall in love.

The question for our age is what pressures will help to shape the movement of people between Britain and Germany and the wider world in the years to come.