Dear Mr Donald Tusk
The people of the United Kingdom of Great Britain and Northern Ireland have spoken via a referendum held on 23 June 2016 and voted in the majority for the United Kingdom to leave the European Union. The official result has been declared and the entire process is deemed to be democratic under the constitution of the United Kingdom.
The mere fact of this referendum result alone should serve as notice under Article 50 of the Treaty of Lisbon amending the Treaty on European Union and the Treaty establishing the European Community of the United Kingdom's intent to withdraw from the European Union.
Unless the Treaty of Lisbon specifically denies notice under Article 50 to be served in the aforementioned manner you should declare that notice has been duly received from the United Kingdom, via the voice of its people, and start the clock for the United Kingdom's withdrawal without further delay.