Boris Johnson will later start forming a government after succeeding Theresa May as Prime Minister.
The new conservative leader will take office on Wednesday afternoon after an audience with the Queen at Buckingham Palace.
After entering Downing Street, he is expected to announce a number of high-profile cabinet posts, including the Chancellor of the Exchequer and the Secretary of the House Secretary.
According to sources close to Mr. Johnson, his top team will reflect "modern Britain."
He should take the opportunity to increase the number of women in full cabinet positions and to strengthen the representation of ethnic minorities.
Mr. Johnson won a decisive victory over Secretary of State Jeremy Hunt in a vote of Tory members ̵
Discussions are to take place between Hunt and Johnson on the next role of the Foreign Minister.
After his victory, Johnson said his priorities were to push through Brexit, uniting the country and defeating Labor leader Jeremy Corbyn.
The ex-mayor of London is expected to speak in front of Downing Street for the first time at 4:00 pm CET after accepting the Queen's invitation to form a government.
Theresa May officially resigns as Prime Minister at Buckingham Palace.
Everything that belongs to a catastrophe?
Boris Johnson's political heritage has everything that belongs to a catastrophe.
He has no common majority. There is no public mandate – remember that this election was only decided by Tory members.
There are political problems in sight everywhere, be it trying to solve the problems of Brexit with a reluctant EU and a divided party, or trying to address deep-seated problems at home.
And just as there is a lot of excitement among his fans that he will finally be number 10, there is skepticism and disbelief in the opposition parties and double-sided concerns in his own party.
Read Laura's full analysis here
What happens when
Wednesday, 12:00 (CET): Theresa May takes part in questions from her last Prime Minister. After lunch, she will hold a short farewell speech outside no. 10 before traveling to the queen to resign.
Boris Johnson will then attend an audience at Buckingham Palace, where he will be invited to form a government.
He will then give a speech on Downing Street before entering the building for the first time as Prime Minister.
Later he will announce his highest cabinet appointments such as Chancellor, Minister of the Interior and Foreign Minister. and will make and receive his first calls from other world leaders.
Thursday: Mr. Johnson is expected to make a statement to Parliament regarding his Brexit strategy and answer questions from MPs. Parliament will split up later for its summer break.
The new Prime Minister will continue to announce his new Cabinet.
Mr. Johnson will inherit a wafer-thin parliamentary majority and, like his predecessor, will continue to rely on support from the Democratic Unionists of Northern Ireland.
Labor, the Liberal Democrats and the SNP have said they will speak out against Mr Johnson over Brexit, although they have stopped threatening an immediate vote of no confidence.
BBC political editor Laura Kuenssberg said that the election of his top team by Mr. Johnson was crucial to his efforts to bring together the belligerent factions of his party.
One of the key decisions he faces is who will take over the treasury after Chancellor Philip Hammond signaled his intention to resign if Mr Johnson became chairman.
The alleged members include Interior Minister Sajid Javid, former Brexit secretary Dominic Raab, and Liz Truss, current deputy to Mr Hammond of the Ministry of Finance.
A number of other ministers, including Justice Minister David Gauke and Secretary of Development Rory Stewart, are expected to make profound changes indicating that they can not report to Mr. Johnson for having decided to join the EU with or without agreement on 31 December. To leave October.
Persons proposed for promotion include Minister of Housing Alok Sharma and Minister of Local Government Rishi Sunak.
Priti Patel may return to the Cabinet less than two years after resigning as International Development Minister for unauthorized meetings with Israeli officials.
And Sports Minister Tracey Crouch, who last year in a dispute with the Treasury Department betting terminals with fixed odds could also be pending for a recall.
A source near Mr. Johnson said: "Boris will build a Cabinet showing all the talents of the party that truly reflects modern Britain."