Let’s be clear: Brexit is bad news for NATO. It will not affect NATO in its core responsibility, because NATO is still NATO and Article 5 is still Article 5. The UK will still be one hundred per cent involved, just as it was before Brexit. Yet the decision made by the British public last week will negatively affect the close relationship between the EU and NATO which the UK had been a key part of.

Brexiteers had promised a return to past glories, driven on by a false sense of nostalgia. But they cannot turn back the clock to a UK as it was 50 years ago. That false promise is the same one Putin is making in Russia, Erdoğan is making in Turkey, and the populists are making across Europe. It simply will not work.

Brexit will diminish the role and standing of the UK on the global stage: The EU will inevitably have to take greater responsibility in the security and defence domain, but Great Britain will not be at the table; EU sanctions against Russia will need to be discussed and possibly extended, but Great Britain will not be at the table; Operations might be necessary and needed by the European Union in Northern Africa, but Great Britain will not be at the table.

Our allies are also worried. The White House has been emphasising the enduring nature of the US-UK special relationship, and given the language, given the shared history, there will always be a close relationship between the UK and the US. Without any doubt, that will stay. Privately, however, there is concern. The UK, whichever way you look at it, was one of the United States’ entries into the European Union. That will now be, unfortunately, a thing of the past.

But Europe will also be diminished, and at the very moment our transatlantic allies have been warning us we cannot keep relying on them for defence. Whichever President is in the White House after November this year, the attitude of the United States will be: ‘Dear European friends, you cannot always ring our doorbell when something goes wrong in your backyard’. There is a clear need for the EU to take more responsibility over security and defence, both inside and outside the direct NATO framework.

There is also a risk that continued political instability will distract Europe from the pressing security concerns it faces from Russia, North Africa, and the Middle East. Brexit will whet the appetite in other nations for their own referenda. We already have, in my own country, the populist Mr Wilders asking for a referendum. In the Netherlands it is legally and constitutionally impossible to hold such a referendum under current legislation, but in other nations it is possible. By gambling on Brexit, David Cameron has turned a problem inside his own Tory party into a huge European problem, for which I blame him completely.

If Europe wants to avoid a long slide into irrelevance, Brexit must therefore trigger a discussion among the remaining 27 about the future. I’m not in favour of blindly chanting the mantra of “Ever Closer Union”. As Jeroen Dijsselbloem, the Dutch Finance Minister and Eurogroup Chair, quite rightly said: ‘When your house is weak, you must think twice before building an extension’. But there is certainly the need for further integration in the fiscal, monetary, and euro domain, and in banking union, the deposit guarantee system, and so on.

First and foremost, however, the European Union will have to find a solution to mass migration. I believe that this was the subject that ultimately triggered Brexit, and it means that external border protection is absolutely key. If we don’t strengthen our efforts in this field, we will lose the Schengen Agreement, just as we have already lost the Dublin regulation.

A generation of political leaders – and I was among them in the not too distant past – have completely underestimated the frustration, the anger, and the uncertainty which our electorates feel towards globalisation, with migration first among their concerns. If we do not control migration in Europe, I think we will be in for a rather rocky future.

So, the building is weak. But I hope Brexit will trigger fundamental discussions on reforming the European Union. In that respect, there might be some silver lining in this dramatic development we’ve seen in Great Britain last week.