UK's relationship with the European Union has never been a bed of roses. In 1975, barely two years after joining, Harold Wilson's Labour government consulted the British population by referendum asking them whether they wanted to remain in the European Community. At that time 67% answered "yes". For the 42 years of membership, taking part in Europe has, for most British governments, comprised preventing Europe's institutions from having too much power and negotiating exemptions and derogations to protect national sovereignty. In 2015 this has led to a UK that has managed to escape both from the single currency and the Schengen Agreements on the free movement of people. There are three areas in which the UK has made a strong contribution to the European Union without playing a wild-card: the creation of the internal market, enlargement and defence. The British have always felt comfortable with a European Union defined as a vast market, but much less so with one of political union. Since a market can never exist without regulation the governments in London have accepted however, whether they have liked it or not, for the European Union to regulate trade, financial services and capital. Hence enlargements have often been viewed as positive extensions to the market. Since UK, along with France, are the only ones to have an army that can project itself outside of the European Union, it has been able to make a significant contribution to European Defence without committing strongly to the institutionalisation of a European Defence Policy, which might have competed against NATO.

In 2015 British political life is marked by a wave of Euroscepticism which is not specific to the country. Most European States are experiencing this trend. Over the last few years an anti-European party, UKIP, has emerged in UK openly campaigning for the country's exit from the European Union[1]. This prospect is shared by a significant number Conservative Party MPs in office at present. Conservative Prime Minister David Cameron, for his part, is convinced that an exit from the European Union would not be a good choice for UK. Under pressure from the Eurosceptics in his party, he has however promised to hold a referendum on the issue before the end of 2017. The question put forward by the independent electoral commission at the House of Commons in September 2015 has the merit of being clear: "Should the UK remain a member of the European Union or leave the European Union?".

David Cameron has to win this referendum by rallying British opinion to the status quo. To do this, he has to provide prior guarantees by re-negotiating the conditions of a status that is extremely particular to UK with the country's partners in the European Union. Renegotiation is a complicated game, meaning that 27 capitals have to be won over. Although the Member States of the European Union are open to re-negotiation so that UK does not leave them, all have set red lines that cannot be crossed. In UK itself, Scotland, which is extremely attached to the European Union, is a constraint that David Cameron has to take on board: in the hands of the independentists, Edinburgh's parliament will revive the issue of independence if the English (and no longer the British) decide to quit the EU. Caught between the Eurosceptics of UKIP and his own party, the Scottish independentists and the other Member States, David Cameron has to play his cards subtly in undertaking renegotiation to see him win the inevitable referendum.

In this paper a panel of European experts from the Centre for International Research (CERI) of Sciences Po and the Robert Schuman Foundation[2] explores all of the issues at stake that will mark UK's future in the European Union over the coming months: what does the British government want? What are its demands? Is the reform desired by London acceptable or not? How far are its partners willing to go to keep the UK in the EU? Is a compromise possible and acceptable to all of those involved? If so, what would the main shape of this be? The referendum result will depend, in part, on the negotiations that occur between London and its European partners and the answers provided to these questions.