Boris Johnson took over as British Prime Minister today, following a meeting with Queen Elizabeth, in a move that puts an outspoken figure out of the European Union at the head of the exit process for the first time since the outcome of the shocking referendum in 2016.

Johnson enters Downing Street amid the gravest situation in Britain's history since the end of the world war, with a split over the EU and weakened by a three-year political crisis since the referendum to break out of the bloc.

Johnson pledged to broadcast energy in the country and complete the exit from the EU by October 31 at whatever cost, which could put the UK in a confrontation with the EU and push it toward a possible constitutional crisis or elections at home.

"We will be leaving the EU by October 31, and we will take advantage of all the opportunities that this will offer in the spirit of 'yes we can' new," Johnson, 55, said on Tuesday after being elected in a vote by Conservative members.

To implement the order, new Prime Minister Dominique Kamens, the official campaign leader for the exit from the bloc, will appoint a senior adviser to Downing Street.

Theresa May Downing Street left three years after a prime minister and her daughter had crises related to leaving the bloc. She will go to Buckingham Palace to formally resign to Queen Elizabeth.

Mai seemed to be soaking up her tears as British lawmakers applauded her as she walked out of the House of Commons. Her government's finance minister, Philip Hammond, resigned on Wednesday before Johnson took over as prime minister.

David Ledington, the acting deputy prime minister, also resigned from the cabinet today.

Johnson is due to enter Downing Street soon and is expected to make a speech before appointing key members of the government, whose choice may be an indicator of how to manage exit from the European Union, Britain's most important decision in decades.

The choice of Cammings, known for his campaign skills but also his controversial style of defying unanimity, points to Johnson's seriousness in stepping up the process of getting out of the bloc and his desire for a top-level politician who took part in the campaign nearby.