Today is officially Brexit. The Prime Minister, Theresa May, has submitted a letter to EU President Tusk to formally notify him of the action. Here is a snippet from that letter (emphasis mine):
Today, therefore, I am writing to give effect to the democratic decision of the people of the United Kingdom. I hereby notify the European Council in accordance with Article 50(2) of the Treaty on European Union of the United Kingdom's intention to withdraw from the European Union. In addition, in accordance with the same Article 50(2) as applied by Article 106a of the Treaty Establishing the European Atomic Energy Community, I hereby notify the European Council of the United Kingdom's intention to withdraw from the European Atomic Energy Community. References in this letter to the European Union should therefore be taken to include a reference to the European Atomic Energy Community.
This is the first I'm hearing of a withdrawal from the European Atomic Energy Community. Was this always part of the plan? Was it possible to leave the EU without leaving the EAEC? If this was a not a given based on last year's Brexit vote, is there a reason why leaving the EAEC was included?