Well, on one level, Article 50 of the Treaty on European Union (part of the Lisbon Treaty) specifies that the Head of State or Government sends a letter to the President of the European Council, and they then set up a negotiating committee to set out the new relationship. They've got two years to get the job done. Simple. On the detail it would vary from quite complicated (we accept to remain in the EEA with broadly that package of benefits and downsides) to extremely difficult – a desire to negotiate the whole relationship on a case by case basis. The most likely outcome, as with any divorce, is that the lawyers would derive the most benefit. But it's definitely possible, and for Eurosceptics, the advantages may well outweigh the inconveniences.