Britain's ambassador to the European Union (EU), Tim Barrow, has handed the official letter triggering Article 50 to Donald Tusk, president of the European Council.
This commences the country's two-year exit process from the trading bloc. Tusk's receipt of the letter was confirmed in a tweet sent by him at 13:29 p.m. Brussels time.
British Prime Minister Theresa May addressed the U.K. Parliament shortly afterwards, telling politicians and the live television audience that the process was underway.
"In accordance with the wishes of the British people, the United Kingdom is leaving the European Union. This is an historic moment from which there can be no turning back," affirmed the PM.
"I choose to believe in Britain and that our best days lie ahead," May added, before emphasizing that the U.K. would seek a path of "sincere cooperation" in its dealings with the EU going forward.
"We will continue to be willing allies, close partners and good friends," said the PM, listing several areas her team has identified as particularly lending themselves to future cooperation between the U.K. and the remaining member states.