Theresa May has been appointed the United Kingdom's second female Prime Minister in a private audience with the Queen at which she was invited to form a government.
Ms May then gave her first speech as Prime Minister outside 10 Downing Street, promising to unite Britain and help the country's struggling working class.
In the biggest surprise, Ms May appointed former London Mayor and Brexit campaigner Boris Johnson as British Foreign secretary, but with Ms May expected to create a new ministerial post focused exclusively on Brexit issues, Mr Johnson may not have much of a role in Britain's future negotiations with the EU.
Ms May's elevation to the country's most senior political role, at the age of 59, completes a whirlwind rise which was triggered by the unexpected referendum vote for "Brexit" on June 23 which brought down predecessor David Cameron.
As Mr Cameron left Downing Street he spoke of his achievements during six years leading Britain.
"Above all it was about turning around the economy. And with a deficit cut by two thirds, 2.5 million more people in work, and one million more businesses, there can be no doubt that our economy is immeasurably stronger."
Ms May "kissed hands" with the monarch in a simple procedure at Buckingham Palace which made her the 13th holder of the post of Prime Minister and First Lord of the Treasury during Elizabeth II's reign.
Ms May arrived at the Palace by ministerial car with husband Philip, having set off from the House of Commons only after receiving the signal that Cameron's resignation as PM had been accepted by the Queen and that he had advised the head of state to appoint the former Home Secretary in his place.
Mr Cameron was accompanied by wife Samantha and children Nancy, Elwen and Florence as he left 10 Downing Street for the last time as Prime Minister.
In a clear bid to define the legacy that he will leave behind him, he spoke of his pride at achievements including reducing the deficit, legalising gay marriage, boosting employment, introducing the National Living Wage, increasing international aid spending and cutting waits for NHS treatment.
And he paid tribute to Samantha, who he described as "the love of my life" who had "kept me vaguely sane". Cameron said he was "delighted that for the second time in British history the new Prime Minister will be a woman, and once again a Conservative".