British Prime Minister Theresa May signed a letter on Tuesday to European Council President Donald Tusk notifying the European Union of the United Kingdom's intention to leave the bloc.
The British ambassador to the European Union Tim Barrow arrived at the bloc's headquarters on Wednesday ahead of the formal handover of the historic letter signed by May.
Barrow will first take part in a scheduled meeting with ambassadors from 27 EU nations before his meeting with Tusk.
May will on Wednesday afternoon notify the UK parliament about the letter that marks the beginning of its formal Brexit divorce.
May also met with cabinet members on Wednesday.
After the meeting, British Foreign Secretary Boris Johnson — who campaigned for the country to leave the EU in last year's referendum — said that it was a "great day".
But, the economic implications of Brexit remain unknown.
While some believe it will be a great economic opportunity for the UK, others believe the kingdom is committing economic suicide.
TRT World's Simon McGregor-Wood spoke to Professor Thomas Sampson of the London School of Economics on how economical aspects of Brexit will impact the kingdom.
Downing Street releases extract of speech
The UK – which joined the European bloc in 1973 – voted to leave the EU in June 2016 in a divisive referendum with 51.9 percent of Britons voting for ‘leave' against 48.1 percent for ‘stay'.
May, an initial opponent of Brexit who won the top job in the political turmoil that followed the referendum vote, will have two years to settle the terms of the divorce before it goes into effect in late March 2019.
Her letter to Tusk will invoke Article 50 of the EU's Lisbon Treaty, launching 24 months of negotiations on the terms of separation and future relations with the remaining 27 EU nations.
In a special address to Westminster on Wednesday, May will acknowledge that the June vote for Brexit had been divisive, but will express hope "that we are no longer defined by the vote we cast, but by our determination to make a success of the result," according to an extract of her speech which was released by her Downing Street office.
"We are one great union of people and nations with a proud history and a bright future. And, now that the decision has been made to leave the EU, it is time to come together," the speech reads.
For the EU, already reeling from successive crises over debt and refugees, the loss of Britain is the biggest blow yet to 60 years of efforts to forge European unity in the wake of two devastating world wars.
Sad day for Londoners
Some Londoners feel sad about the prospect of Brexit.
''Theresa May has just inherited something, got her head down and not questioned it at all, implementing it, so yeah — bad day," Flora Joll said.
London voted to remain and so understandably people heading to work think of Wednesday as a sad day.
''I work in central London and I think we have so many people from different countries, different cultures here and I think that's how it should remain, so for me it is a sad day.
"Mostly it was older people who voted for Brexit and it will be young people who have to live with it in the future. I think it's a disastrous move," Christopher Jack said.