The most difficult obstacle to the Brexit negotiations is not financial compensation, but the border with Ireland and the nature of the British economy, says Ian Manners, an expert on European integration at the University of Copenhagen. 

LN Denmark, like the Czech Republic, is not a member of the euro area and some opt outs have been negotiated within European Union integration. You are not worried that in the light of Brexit and reform proposals of the French President Emmanuel Macron our countries will find themselves on the periphery Union?
- Yes, the fear is very real in Denmark. Although Denmark is not a member of the euro area, the Danish crown is firmly tied to the euro. Whenever the euro exchange rate moves, we must adjust the Danish crown. In addition, in the past, Denmark has always participated in reforms aimed at the banking union. Macron's proposals for establishing the office of European Finance Minister and European Monetary Fund therefore have far-reaching consequences for Denmark. On the other hand, however, there is less risk of eurozone collapse and another debt crisis, which is also important for Denmark, similarly to the Czech Republic.

LN For the Danes and Czechs, Britain was often an ally. Will we then be weaker after Brexit?
- Yes, people often perceived the UK as a friend in both countries. It is always good to have a large Member State with whom you can cooperate. But the British were not always the best friend. If there was something in the Czech or Danish national interest, and at the same time it was not important to the British, they helped only rarely.

LN Do you have a concrete example for this statement?
- Yes, take the EU enlargement. Both Denmark and the United Kingdom were big supporters of enlargement, but both countries held very different attitudes. Denmark thought that very long transition periods would apply to new members, but the British view was that transition periods were not at all needed. Another example is the Danish effort to be as close as possible to the decision-making process within the euro area. Denmark is tied to the euro, a difference from Britain, and more exposed to the problems of the eurozone. Denmark is, therefore, interested in greater regulation of the banking system, which Britain had a strong opposition to. Therefore, the Czech and Danish banks have not been helped by the British approach during the 2011-2013 crisis.

LN How do you look at the Danish opt outs - especially the absence from the eurozone and the EU's defence policy? In the country, a few years ago there was a debate about whether opt outs should be lifted. Now Denmark has not engaged in enhanced defence cooperation…
- Returning to 2008 when I worked for the Danish Institute of International Studies and led a large team that wrote a comprehensive report on the consequences of our four opt outs. At that time, there was support in Denmark for joining defence and justice cooperation, but not the euro and citizenship. But the Irish voted in a referendum against the European constitution and the whole process was frozen. The Danes voted later held a referendum on whether to maintain an opt out in the area of justice and home affairs. Most people had no idea what was at stake, and voted against. Not surprisingly, it's a very complicated area.

LN Let's go back to defence...
- Here the Danish attitude is even more complex than in the euro area. Denmark sees itself as an positive player in European defence. Since the prime ministership of Anders Fogh Rasmussen, Denmark has sought to play a more interventionist role and joined the coalition in Iraq and Afghanistan. He also tried to be at the forefront of naval defence and, as Britain was an active member of NATO, the opt out in defence became more and more problematic. Now we have strengthened cooperation under PESCO, and Denmark cannot join for constitutional reasons, even if 80 percent of the parties in Parliament agree. That is why they would need to call a referendum to allow Denmark to join the PESCO.

LN What is the main argument of those who oppose involvement in PESCO?
- These are somewhat similar to arguments against the Maastricht Treaty. People do not want to engage in enhanced cooperation that could lead to the creation of a European army, which would not be good for the North Atlantic Alliance. The European cooperation will, of course, help NATO against real- or cyber-threats. Trump expresses an unwillingness to help us against the dangers from the East. It is not about weakening NATO, but about what the North Atlantic Alliance cannot do. For a referendum, however, this would be a very complex issue, just as in the case of justice and home affairs. Danes generally tend to be conservative and say no to change.

LN You mentioned the danger from the East. Is there a threat from Russia, even in Denmark, which is not part of EU security and defence cooperation? Is this question solved in your country similarly to the Baltic States or Finland?
- Yes, it's similar, because of the Russian flights over the Baltic Sea. If I remember correctly, Danish jets had to intercept Russian Federation military aircraft over Baltic. This is a real risk, especially for anti-aircraft defence. We have already experienced cyber-activism in order to influence public opinion, whether it concerns Brexit, France or Germany. It is a constant threat, and I would not be surprised to see it in Denmark.

LN Let's go back to Brexit. Can you imagine a rational solution to the dispute over Northern Ireland?
- To be honest - I cannot. In 2013, UK Secretary of State David Lidington arrived in Denmark to sell David Cameron's plans to reform the UK's relationship with the EU. Previously, he was also the shadow minister for Northern Ireland. I told him at that time that it would cause huge problems for the peace process. There are two solutions: the first is simply to impose a border with Ireland, but to do some ‘light’ version. This is not easy, as it seems that Britain will not join the customs union. The second option is to refrain from imposing a border - in which case you will have customs controls between Northern Ireland and the rest of the UK. Neither of these solutions is good and both endanger the peace process in Northern Ireland. Things have changed in Northern Ireland over the last 30 years, and this area has become richer, but many things have not changed and there is still a lack of trust between the two communities. Political risk and the associated violence is therefore real.

LN Do you therefore consider the Northern Ireland question as the most difficult thing in the Brexit negotiations?
- Yes, people do not admit it. Many of the big problems have not yet been discussed in the media. The biggest challenge is not financial compensation, not even the issue of EU citizens in Britain and the British in the EU. It is rather the fact that the UK economy is based on services - financial, tourism, media, etc. There has never been a trade agreement in the world that would give services the same conditions as the EU Single Market. For example, if the UK introduces a tourist visa - the British do not want the tourists to overstay - it will be a complete disaster.