European Council President Donald Tusk shows British Prime Minister Theresa May’s letter as he holds a press conference after his meeting with British Prime Minister Theresa May’s Britain’s ambassador to the EU Tim Barrow (not seen) in Brussels on March 29, 2017. British Ambassador to the EU Tim Barrow delivered a letter, signed by British Prime Minister Theresa May, to European Council President Donald Tusk to trigger the Article 50 of the Lisbon Treaty that starts the official exit negotiations of U.K. from EU. (Photo by Dursun Aydemir/Anadolu Agency/Getty Images)

