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During dinner we will discuss the UK issue, to see if we can pave the way for an agreement in February. As I set out in my letter, we have achieved significant progress in negotiations; however we are still far from an agreement on several topics. This Thursday we will need to focus especially on the most controversial ones. The stakes are so high that we cannot escape a serious debate with no taboos.
The wording of the letter is very interesting. The fact that Tusk has said that there should be no taboos seems to imply that he is willing to at least contemplate all of Cameron's renegotiation demands, including the big one - restricting the free movement of people.
In a letter Cameron sent to Tusk last month, he said that Britain needs to be able to exert greater control on the arrival of immigrants from inside the EU. He is struggling, however, to win over support for his plans from other European leaders such as Polish prime minister Beata Szydlo who said last week that she and Cameron do not see "eye to eye."
Tusk's invitation comes on same day that an ICM poll was released, showing that the majority of the British public think they will vote to leave the EU if Cameron does not manage to restrict the free movement of people in some way.
The prime minister's job has been made even harder by a report that was released on Tuesday by the Commons' European Scrutiny Committee. It says that the only way that public can trust that Cameron's renegotiation demands have been met is if there new are treaty amendments or protocols that enshrine them in law. These can only be achieved if every single member of the EU agrees to them using their own constitutional procedures. In some countries, this will mean holding a referendum.
It's going to be a very interesting dinner.