In 2016 David Cameron called a referendum over the UK's possible exit from the EU with one sole objective - to end the division among the Conservatives and unite them once and for all on European issues. It backfired and today his party is more divided than ever. When the prime minister lost, the shared fear around the entire continent was that Brexit would divide the European Union. Two and a half years on, the UK's possible departure from the EU on 29 March has weakened the European project, but much less than expected.
This is the first time that a member state has chosen to leave, and what's more, an important EU partner. However, among the remaining 27 members, there is a notable unity of action to contain the damage. The country that will really suffer from the split is the one that leaves. The financial and business costs have yet to be calculated, but in any case they will be hefty. It depends on whether in the end the exit takes place with a deal or not, and what kind. But the magnitude of the possible material damage, and also the loss of "soft power", or ability to attract, is incomparable to the negative impact the United Kingdom's constitutional system. And here is the greatest paradox: on leaving the EU, the British people will see their unity and their unwritten constitution directly under threat. The slogan of the cheerful Brexiters was the exact opposite: they wanted to "take back control".
The internal balance among the four nations and the guarantee of territorial cohesion are being lost along with the anchorage of integration in Europe. In Northern Ireland there is a growing feeling in favour of unification with the rest of the Irish. This comes in response to the problems after Brexit to preserve the Good Friday peace agreement made in 1998, which demands a completely open border on the island and is based on the application of European law in two member states that share a market.
In Scotland, MPs from all parties are calling for the same treatment offered by Brussels to Northern Ireland: to be more connected to the Union in terms of free circulation of goods than the rest of the UK.
If they don't achieve this the Scottish nationalists could speed up their demands for a new independence referendum, with the double aim of gaining independence and then joining the EU, an argument that is more difficult to fight from London.
The exit from the Union is not just a terrible business move; it is also a threat to the constitutional system of the most venerable democracy in the world. Historian and columnist Timothy Garton Ash sums up the different options on the table up to the last minute of negotiations with these words: "The only good Brexit is no Brexit."