Research

"As the text currently stands, the safeguard mechanism on benefits may be challenged in the courts," said Charles Grant, of the Centre for European Reform. "Cameron needs to secure a promise that this mechanism will be included in the treaties when they are next changed. It is crucial that he finds a way of persuading the Poles to agree."

"I'm a bit hesitant to give the renegotiation too much weight, the reason being that the changes Cameron can secure are relatively minor," Christian Odendahl, chief economist at the CER told DW."I think the results of the renegotiation matter only insofar as they can be portrayed as a success. Cameron and his advisers will of course claim that he has secured a good result, while the die-hard euroskeptics will say the opposite."

Agata Gostyńska, EU affairs analyst at the Centre for European Reform, said Poland had to show resistance because being seen as too accommodating risked backfiring with domestic opinion. "For the moment it seems there is enough flexibility in the text for both to claim some victories. But the devil is in the details, and what Cameron and Szydlo will be discussing."

"The proposed reforms still need to be adopted by the Council – and they are humble," says Rem Korteweg, senior researcher at the Centre for European Reform. Most will not dramatically change the way in which the EU operates. There are some cosmetic changes which are very important to British politics – such as the proposal to exclude the UK from 'ever closer union.'

"The two questions of freedom of movement for people and freedom of movement for commerce are not necessarily related," said Camino Mortera-Martinez, a research fellow at the Centre for European Reform. "But the closing of the border would create enormous obstacles to trains and trucks."

Charles Grant, director of the CER, says the emergency brake is fraught with difficulties. "British officials want to be able to use the brake immediately. Yet the mechanism could well require EU legislation, which often takes more than a year. Second, according to what criteria would use of the brake be permissible? The British will want the criteria to be vague enough for them to be able to pull it easily; the commission and other member states will try to make the criteria objective and hard to satisfy."