Earlier this week, French President Emmanuel Macron attended the opening of the Paris headquarters of JPMorgan, an American investment bank. Although Mr Macron started his professional life as a banker and therefore may be assumed to retain some interest in this sector, it still seemed odd that a busy head of state would find the time to cut the ribbon for a bank building.

And yet, this was no ordinary event. JPMorgan had long used London as its financial gateway to the European Union and its shift to Paris was its response to Britain's decision to leave the EU.