- Boris Johnson is the new British PM after he asked for Queen's permission to form a government
- Protesters attempted to block his car's route along the Mall but were bundled aside
- Theresa May spoke for the last time as PM outside No 10
- Philip Hammond has quit as Chancellor, the most high profile in a slew of resignations
Boris Johnson became the new British Prime minister after he asked the Queen for permission to form a government. He was earlier invited to the Buckingham Palacce by the Queen in a tradition known as "kissing hands".
Johnson said the UK "will come out of the EU on October 31st — no ifs, no buts".
Speaking at No. 10, Johson said: "The time has come to act, to take decisions, to give strong leadership and change the country for the better."
"We in this government will work flat out to give this country the leadership it deserves."
Boris Johnson says work "begins now" as he enters 10 Downing Street as Brisith prime minister for the first time.
He said: "After three years of unfounded self doubt, it is time to change the record". Johnson added that in preparation "for a post-Brexit future, it is time we looked not at the risks, but the opportunities that are upon us."
"Do not underestimate our country," said Johnson. He is set to announce his most senior Cabinet appointments.
As prime minister, Johnson said he will "take personal responsibility" for delivering change.
Backstop plan 'undemocratic'
As the new PM, Johnson calls the backstop plan to avoid a hard border in Ireland after Brexit "anti-democratic". A "backstop" is a baseball term that refers to a "safety net". It is key to talks over the future of the Irish border after Brexit.
The border between the Irish Republic and Northern Ireland (part of the United Kingdom) will be the only land border between the UK and the European Union. In theory, there should be checks on items crossing the border after Brexit.
But the "backstop" would bring back memories of 30 years of conflict in Northern Ireland — and checkpoints could become a target. The UK and the EU hope to agree on a trade relationship in the future that keeps the border as open as it is now.
Johnson defeated Jeremy Hunt in the Tory leadership contest by 92,153 votes to 46,656.
Earlier, former PM Theresa May delivered a farewell speech in Downing Street before she tendered her resignation to the Queen.
May gave her final speech in Downing Street — her husband Philip alongside her — before heading to Buckingham Palace.
She said serving as prime minister had been "the greatest honour" and thanked all those who had worked with her.
May wishes Johnson well
She wished new Prime Minister Boris Johnson and his government well, adding: "Their successes will be our country's successes."
Earlier, May faced MPs' questions for the final time and looked visibly emotional as she left to applause.
What happens next
Johnson will speak outside No. 10 too, before announcing several senior Cabinet appointments.
He is expected to use the opportunity to increase the number of women in full Cabinet positions and boost the representation of ethnic minorities.
During his journey to Buckingham Palace to accept the Queen's invitation to form a government, Johnson's car was briefly held up by protesters from Greenpeace, who formed a human chain across The Mall.
Johnson's choice of his top team is critical in his efforts to bring the warring factions of his party together, according to BBC's Laura Kuenssberg.
Johnson is resolute that his leadership rival should not stay on at the Foreign Office, but Jeremy Hunt is firm that he won't accept anything less than his current role — or becoming home secretary, chancellor or deputy prime minister — and considers other moves a demotion.
Kuenssberg said it is a risky decision for the new PM — forcing Hunt out would be a bad move in terms of uniting the party, but giving in to his refusal to budge is a challenge to his authority.