A series of developments in the UK and the European Union have led to a situation where Britain is preparing for a referendum to decide whether to leave or stay in the union.
Most clearly, Prime Minister David Cameron committed the Conservative Party, during last year's elections, to renegotiate Britain's relationship. This would be put to the British people in a referendum. Wider political pressure was mounted for other party leaders to make similar commitments. Recent opinion polls point to strong and growing support for withdrawal.
While we should be careful not to assume the UK is destined to withdraw, the possibility of this happening is now stronger than ever before. A UK withdrawal would have profound implications and costs for UK, far greater than for EU.
Nevertheless, the rest of Europe would face both the unprecedented event of a withdrawal of a member state and, in the case of the UK, the withdrawal of one of its largest members. This could bring about significant changes to EU. For some, the loss of one of the most economically liberal members could tip EU towards protectionism, or perhaps trigger a crisis in European integration leading to EU's unravelling.
Others see an opportunity for the EU to free itself of its most awkward member, making the EU easier to lead, aiding a solution to the Eurozone's crises, in turn strengthening the foundations of an ever closer union among the people of Europe.
As such, potentially more dramatic and damaging events – potentially far more than a renegotiation – in the development of EU are being under discussed. The threat of a withdrawal also underpins Cameron's hopes to secure a renegotiation of Britain's relationship within EU. As such, there is a need for better analysis of the possible implications of a withdrawal.
A British withdrawal would trigger three interrelated series of challenges to the EU. First, there is the problem of how to manage the process of a British withdrawal, a member state withdrawing from EU was somewhat a taboo. To a certain extent this remains so. Despite the inclusion of article 50 in the Treaty on European Union, setting out a withdrawal process, the procedure is something of an unopened Pandora's Box.
Negotiations would not only take place between UK and EU. Negotiations would need to take place within the union to amend EU's institutions, voting allocations, quotas and budgets - issues rarely settled with ease.
The second problem is how to shape ongoing EU co-operation and integration around a British withdrawal. The absence from EU's formal decision-making structures of one of the largest and arguably one of its most influential member states could change the balance of power within EU. This would in turn change its nature and direction.
Even with Britain out of the room, the EU has still struggled to find the necessary solidarity and leadership to manage the Eurozone crisis. The Eurozone crisis itself is both exacerbating Britain's feeling of detachment from EU, while also distracting attention by the rest of Europe from the possibility of a British withdrawal.
The final problem is how EU should manage relations with UK after a withdrawal. Article 50 requires any withdrawal agreement include a framework for future relations with the withdrawing state. Despite what British Eurosceptics and Britain's critics in the rest of the EU might wish, Britain and EU will remain deeply interconnected. A withdrawal could never mean the end of Britain in Europe, only of UK's membership in the EU.