Britain's Prime Minister David Cameron leaves 10 Downing Street, in London to face prime minister's questions for the last time Wednesday, July 13, 2016.
By convention the Queen is above party politics and does not personally choose the prime minister, so Mr Cameron's last duty was to advise her to invite Theresa May to form the next administration.
Making an ambitious statement outside 10, Downing Street after returning from Buckingham Palace as the prime minister, May committed herself to protect the "precious bond of the United Kingdom", considered a challenge in the context of the Brexit vote and demands in pro-EU Scotland for another independence referendum.
British Prime Minister David Cameron on Wednesday said serving as Prime Minister was his greatest honour.
May became Britain's second female prime minister in history, after Margaret Thatcher.
Just moments after the former Conservative leader's departure from the Palace, a auto carrying his successor arrived.
He said: "We've today had warm words from our new prime minister about the need to stand up for more than a "privileged few". "This morning I had meetings with ministerial colleagues and others, other than one meeting this afternoon with Her Majesty, the queen, the diary for the rest of my day is remarkably light", Cameron said, to laughter from lawmakers.
Britain's Conservative Party has confirmed that Theresa May has been elected party leader "with immediate effect" and will become the country's next prime minister.
Mrs May's elevation to the country's most senior political role, at the age of 59, completes a whirlwind rise that was triggered by the unexpected referendum vote for Brexit on June 23 which brought down her predecessor.
May had been a supporter of the campaign to keep Britain within the European Union but has indicated that she intends to honor the wishes of the British people and to take the country out of the bloc by invoking Article 50 of the Lisbon Treaty.
May has said that she plans to form a different government department which will lead the process of Britain's exit from European Union and she plans to appoint a "Leave" campaigner to head it. "I came into Downing Street to confront our problems as a country and lead people through hard decisions so that together we could reach better times".
Earlier, Mr Cameron held a final rowdy and mainly good humoured Prime Minister's Questions in the House of Commons.
She will name her own frontbench team after taking office.