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.