LONDON, March 29. /TASS/. UK Prime Minister Theresa May has signed a formal letter to notify the European Union leadership that London was formally launching the procedure of quitting the organization, according to a photo released late Tuesday by the UK media.

The image shows May at the table in her official office in London. The letter, that has several pages, will be delivered personally to European Council President Donald Tusk on Wednesday by the UK ambassador to the EU, Tim Barrow.

The official notice will trigger Article 50 of the Lisbon Treaty, starting a two-year period of negotiations on terms and conditions of Brexit.

May will also make a speech before the Parliament on Wednesday at approximately 12:30 GMT (14:30 Moscow time).

On Tuesday evening, the prime minister called German Chancellor Angela Merkel, President of the European Council Donald Tusk, and President of the European Commission Jean-Claude Juncker "to update them ahead of the letter giving notification of the UK’s intention to withdraw from the European Union being delivered tomorrow," May’s office said in a statement.

"In separate calls, they agreed that a strong EU was in everyone’s interests and that the UK would remain a close and committed ally," the statement reads. "They also agreed on the importance of entering into negotiations in a constructive and positive spirit, and of ensuring a smooth and orderly exit process.".