Image copyright PA David Cameron will leave Downing Street for the final time as PM later, with Theresa May waiting to replace him.
Mr Cameron has been taking part in his final Prime Minister's Questions, before heading to Buckingham Palace to tender his resignation to the Queen.
He told MPs his time in power had been "amazing" and joked that apart from his royal audience his "diary for the rest of the afternoon is remarkably light".
After taking office, Mrs May will set about naming her own frontbench team.
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The current home secretary, 59, was the only remaining candidate in the Conservative leadership contest following Andrea Leadsom's withdrawal on Monday.
The contest began when Mr Cameron, who has been prime minister since 2010, announced he would step down after losing the EU referendum in June.
Image copyright ReutersDuring a generally light-hearted and jocular session of Prime Minister's Questions, his 182nd as PM - Mr Cameron said he had answered 5,500 questions at the despatch box.
'Amazing moments'
Defending his economic, social and foreign affairs legacy, Mr Cameron said there had been "many amazing moments" over the past six years of "public service in the national interest".
Mr Cameron "warmly congratulated" Theresa May, who sat next to him during the session, on her election and told Labour leader Jeremy Corbyn that "when it came to female prime ministers I am glad to say the score will soon be two-nil".
Mr Corbyn said that although he had often disagreed with the PM, he thanked him for his service over the last six years and praised him for his backing for equal marriage and his efforts to secure the release of Shaker Aamer from Guantanamo Bay.
The Labour leader also paid tribute to Mr Cameron's wife Samantha and his family, who watched the proceedings from the public gallery. His daughters Nancy and Florence were seen to give their father a wave and cheer him on during the session.
Earlier, Mr Cameron told the Telegraph he came into Downing Street to "lead people through difficult decisions so together we could reach better times", adding "as I leave today, I hope people will see a stronger country, a thriving economy, and more chances to get on in life."
Later, after saying goodbye to staff at Downing Street, the PM will tender his resignation to the Queen,
Royal audience
The BBC's Royal Correspondent Nicholas Witchell said the private audience was likely to be a short one, potentially about twenty minutes.
Soon after, Mrs May will then make her own way to Buckingham Palace, accompanied by her husband Philip, when she will be asked to accept the monarch's offer to form a new government.
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Our correspondent said Queen Elizabeth was likely to ask the new PM, who will be the 13th leader of her reign, about her "intentions and programme" for government.
Mrs May will then return to No 10 as the country's second female prime minister, following in the footsteps of Margaret Thatcher.
She is expected to briefly address the nation before meeting top officials, including Cabinet Secretary Sir Jeremy Heyward, and receiving a full national security and defence briefing.
She will be asked to hand-write letters to the commanders of the UK's four Trident submarines about what to do in the event of a catastrophic nuclear attack on the UK and to appoint two nuclear "deputies" - ministers who will take decisions on the deterrent if she has been rendered incapable.
She is also expected to take calls from a number of foreign leaders. Later on Wednesday, she will get down to the work of putting together her government - with key appointments set to be announced within hours.
Factfile
- David Cameron held office for six years, 62 days
- This makes him the UK's 22nd longest-serving prime minister
- Aged 49, he will be the youngest PM to leave office since the Earl of Roseberry in 1895
- Theresa May, at 59, becomes the oldest incoming prime minister since Jim Callaghan in 1976
Removal vans were spotted outside Downing Street on Tuesday, as Mr Cameron's ministers paid tribute to him in his final cabinet meeting.
Former Culture Secretary Maria Miller rejected suggestions that Mr Cameron's legacy would be totally defined by the decision to leave the EU, saying that while this seemed "a very big part of the political bubble" now, other achievements would endure.
She told Sky News the prime minister has "championed gay marriage and social justice while putting the Conservative Party in the centre ground" of politics and leaving behind a "strong economic foundation" to cope with the uncertainty caused by Brexit.
The swift transition of power comes after the expected nine-week leadership campaign was truncated to just a couple of days by leading Brexit campaigner Andrea Leadsom's surprise withdrawal.
Image copyright Getty ImagesMrs May, who backed a vote to remain in the EU, will unveil her full ministerial team over the next couple of days, with the focus on the key positions of chancellor and foreign secretary as well who will be put in charge of leading the Brexit negotiations.
She is expected to promote a number of women to senior positions, with International Development Secretary Justine Greening and Energy Secretary Amber Rudd among those likely to get upward moves.
Asked her about her prospects, Ms Rudd told reporters: "I haven't been told anything yet so I'm just going to get on with my day job".