Guy Verhofstadt. Yves Herman/Reuters Just a few months ago, Guy Verhofstadt was a name that was most likely lost on any Brit who didn't boast an impressive knowledge of European politics.

Now, the former Belgian prime minister is being talked about by the British press on an increasingly frequent basis.

That is because Verhofstadt is one of the European Union's most important figures. He sits in the European Parliament as leader of a powerful centre-left coalition, but more recently he was chosen as the chief Brexit negotiator ahead of Britain's official departure from the 28-nation bloc.

A federalist who is a staunch defender of the EU, Verhofstadt has written a book, "Europe's Last Chance: Why the European States Must Form a More Perfect Union," in which he argues that the EU must reform itself to overcome current crises and survive into the coming decades and beyond. In the book, scheduled for release on January 3, he says the Brexit vote was a symptom of an EU in need of radical change.

Brexit proponent Nigel Farage said the European Parliament's decision to appoint Verhofstadt as its chief Brexit negotiator was tantamount to a "declaration of war" on a "sensible" negotiation process. On Friday, we spoke with the former Belgian prime minister about Britain's decision to leave the EU, what British Prime Minister Theresa May could expect to achieve in Brexit negotiations, and his vision for how the EU could be improved.

Business Insider's Adam Payne: Can you briefly explain what your role will be in Brexit talks?

Guy Verhofstadt: The withdrawal agreement and new agreement regarding the EU's new relationship with Britain needs to be approved by the European Parliament.

The Parliament has nominated me to coordinate negotiations, to have a point of view in these negotiations. We want to be involved from day one once the negotiations start because at the end we need to give approval for both things: the withdrawal agreement and a new relationship.

Payne: How difficult will it be for the EU and Britain to come to an agreement?

Verhofstadt: It's difficult to say until Article 50 is triggered by the British authorities and we can start negotiations.

What is key for the European Union is not undo the internal market and the so-called four freedoms. We are also going to try to strengthen the Union, to use this exercise to strengthen the Union in a number of ways. The main approach of the European Parliament will be looking to protect the interests of citizens of the EU. It's their interests that we need to defend as their representatives.

The basic position of all the institutions in Europe is very clear: The four freedoms are bound to each other. The internal market is based on four freedoms — not three, or two.

Payne: So there is no chance of Britain curbing EU immigration while retaining membership of the European single market? That's the sort of deal some ministers have hinted at ...

Verhofstadt: The basic position of all the institutions in Europe is very clear: The four freedoms are bound to each other. The internal market is based on four freedoms — not three, or two. Goods, services, capital, and the free movement of people. You cannot separate them. I think this is a perfectly firm and clear position for everybody.

It's easy to say, "Yeah, we want a special passport for people working in our services to go and work in Europe," for example, but the opposite, like the possibility of Polish people to work on a construction site in London, is not possible. This just doesn't make any sense.

Payne: Surely, this means Britain is heading for a hard Brexit?

Verhofstadt: We have to wait and see what the position of the British government is at the moment of Article 50 being triggered. How it will develop itself is down to the what the Supreme Court says about it. It is clear that the European Parliament has the final say, but the British Parliament will have a role to play, too. Let's wait for that.

When we get to that point, they will ask for something, we will say yes or no. First, Britain needs to define its position.

Payne: Some people have suggested that the EU intends to give Britain a "bad" deal in order to deter other member states from leaving in the future — is this true?

Verhofstadt: It is not a question of a bad deal. If a country wants to go out, they go out. It's their decision. But it's important that we look to the interests of the 48% people who didn't vote out. How are we going to do this? I don't know.

It is not a question of a bad deal. If a country wants to go out, they go out. It's their decision.

The main thing, in my opinion, is that Brexit is an opportunity to reform the Union in a way which will make it more effective and stop countries wanting to break away. It is an opportunity to end a system which has been in place for over 20 years now, whereby there are 28 unions, not one. An old system where each member picks and chooses which policy they like.

There is a belief that we are going to give a bad deal to a country so other countries don't follow the same direction. The challenge we actually face is completely different. This negotiation is about reforming the EU in a way that makes it an actual union, something that hasn't been the case for quite a long time now.

What I do in "Europe's Last Chance" is examine the problems with the Union and how Brexit can be a chance for reforms which can help repair them.

Payne: What did you think of the Leave and Remain campaigns? Why was Leave successful?

Verhofstadt: The Leave campaign purely used migration and specifically the fear of migration as their main argument. The Remain campaign tried to use the negative economic fallout as their main argument.

The more emotional and geopolitical arguments for Britain remaining in the Union were never raised during the whole campaign. The most negative thing about Brexit is on the geopolitical level. Imagine that you wake up in the morning as a political leader in Beijing and you hear Britain has walked away from the European Union — you'd be saying, "Oh wow, that's the weakening of European countries." The negative geopolitical consequences were never discussed.

But every analysis we can make now of what the Leave and Remain campaigns did or didn't do is history. It's the future that's important.