LONDON, March 29 -- The Britain on Wednesday officially started the historic process to leave the European Union (EU) as the letter signed by Prime Minister Theresa May is sent to leaders of the bloc.

It is "an historic moment from which there can be no turning back," May told the House of Commons. "We will be after a bold and ambitious free trade agreement with the EU."

May addressed a packed House of Commons at Westminster as the Ambassador to the EU Sir Tim Barrow personally handed the letter to Donald Tusk, president of the European Council, Wednesday noon. It starts a two-year period of negotiations on a future relationship between Britain and the EU.

Giving official notice under Article 50 of the Lisbon Treaty, the letter means the exit process is underway.

The move came nearly nine months after the British voted for Brexit by a margin of 51.9 percent to 48.1 percent in a referendum last summer.

By triggering Article 50 of the Lisbon Treaty, the Britain and EU is expected to have a two-year process in which the terms of exit will be negotiated. Unless both sides agree to extend the deadline for talks, the UK will leave on March 2019.

Article 50 refers to the formal procedure by which an EU member state notifies the European Council that it intends to leave the block.

This sets the clock running, and allows two years for Britain and the EU to discuss exit arrangements. After that, an exit happens, whether matters are settled or not.

But if Britain's departure from the EU takes place without a formal agreement or a transitional arrangement, there could be negative implications for British trade and services with the EU, and for EU services and trade with Britain.

In her statement in the Commons, May told MPs that the official start of Brexit marks "the moment for the country to come together."