Boris Johnson has been appointed Britain's new Foreign Secretary in a shock development, as Theresa May builds her new Cabinet.
She named Philip Hammond as her new Chancellor and sacked George Osborne in a historic evening in Westminster less than two hours after she was officially sworn in as the UK's second female Prime Minister.
Amber Rudd was appointed the new Home Secretary, a job made vacant after Mrs May left the department after six years in charge. Long-time Eurosceptic Tory David Davis has been handed the big role of chief Brexit negotiator, a new Cabinet position.
Fellow Brexit campaigner Dr Liam Fox returned to the Cabinet tonight after four years of absence as he was named the Secretary of State for International Trade - another new post and a key role following Britain's vote to leave the EU.
Mr Osborne was brutally sacked by Mrs May, bringing an abrupt end to his six years in charge of the Treasury. There were also reports that all of David Cameron's political advisors had left Downing Street - a sign Mrs May is determined to break with the past.
The early developments of Mrs May's first hours in charge are a clear sign of Mrs May's attempts to unite the Conservative party after months of bitter infighting during the EU referendum campaign.
By bringing in several high profile figures from the right of the party - including Mr Davies and Dr Fox - Mrs May has handed an olive branch to Brexit supporters who feared she would backtrack on leaving the EU having campaigned on the Remain side.
In other developments tonight, Michael Fallon was re-appointed Defence Secretary, while Mrs May's close ally and leadership campaign manager Chris Grayling was yet to be handed a new job and remains as Leader of the Commons for now.
There were signs earlier this week that Mrs May would not include Mr Osborne in her new government. She used a key speech on Monday to promise a major break from Mr Cameron and Mr Osborne's economic policy, promising to deliver "serious social reform".
But it nevertheless came as a big shock in Westminster tonight that the man in charge of the economy for the last six years wasn't even offered a role in the new-look Government.
Mr Hammond moves to the Treasury after serving as Foreign Secretary for more than two years. The father of three is expected to take residence in the flat above Number 11, where the Cameron family has been living for the last six years.
The Camerons swapped residencies with the Osbornes because of their larger family. But with Mrs May and her husband Philip having no children, the Hammonds are likely to take the bigger flat.
Setting out her stall as a "one nation" Tory outside No 10 after being sworn in as the UK's new Prime Minister by the Queen during a short trip to Buckingham Palace this evening, Mrs May pledged to battle "social injustice" and create a "country that works for everyone".
Speaking outside No 10 this evening after being appointed Britain's second female Prime Minister, Mrs May said: "The Government I lead will be driven not by the interests of the privileged few but by yours.
"We will do everything we can to give you more control over your lives. When we take the big calls, we will think not of the powerful, but you."
Mrs May became Britain's second female premier, following in the footsteps of fellow Tory Margaret Thatcher, after a 34 minute audience with the Queen in Buckingham Palace. The monarch invited her to form a government just minutes after Mr Cameron had been in to tender his resignation.
She went on: "Not everybody knows this, but the full title of my party is the Conservative and Unionist Party. That word Unionist is very important to me.
Mrs May said: "It means we believe in the Union, the precious, precious bond between England, Scotland, Wales and Northern Ireland. It means something else that is just as important.
"It means we believe in the Union not just between the nations of the United Kingdom but between all of our citizens, every one of us, whoever we are and wherever we are from."
Mrs May said being a "unionist" was not just about protecting the UK, but representing everyone who lives here.
"That means fighting against the burning injustice that if you are born poor you will die on average nine years earlier than others," she said.
"If you are black you are treated more harshly by the criminal justice system than if you are white."
She went on: "If you are a white working class boy, you are lless likely than anybody else in Britain to go to university.
"If you went to state school, you are less likely to reach the top professions than if you are educated privately.
"If you are a woman, you will earn less than a man.
"If you suffer from mental health problems, there is not enough help to hand.
"If you are young, you will find it harder than ever before to own your own home."
Mrs May said the "mission to make Britain a country that works for everyone means more than fighting these injustices".
"If you are from an ordinary working class family, life is much harder than many people in Westminster realise," she said. "You have a job but you don't always have job security. You have your own home but you worry about paying the mortgage.
"You can just about manage but you worry about the cost of living and getting your kids into a good school.
"If you are one of those families, if you're just managing, I want to address you directly.
"I know you are working around the clock, I know you are doing your best, and I know that sometimes life can be a struggle.
"The Government I lead will be driven not by the interests of the privileged few but by yours.
"We will do everything we can to give you more control over your lives.
"When we take the big calls, we will think not of the powerful, but you.
"When we pass new laws, we will listen not to the mighty, but to you.
"When it comes to taxes, we will prioritise not the wealthy, but you.
"When it comes to opportunity, we won't entrench the advantages of the fortunate few, we will do everything we can to help anybody, whatever your background, to go as far as your talents will take you."
Delivering a warning about how tough process of Brexit could be, Mrs May said: 'We are living through an important moment in the country's history.
"Following the referendum we face a time of great national change. I know because we are great Britain, we will rise to the challenge.
"As we leave the European Union, we will forge a bold new positive role for ourselves in the world.
"And we will make Britain a country that works not for the privileged few but for every one of us.
"That will be the mission of the Government I lead and together we will build a better Britain.'
Mrs May paid tribute to Mr Cameron for his work tackling the deficit and getting people into work.
"I follow in the footsteps of a great modern Prime Minister. Under David's leadership, the Government stabilised the economy, reduced the budget deficit and helped more people into work than ever before,' she said.
"But David's true legacy is not about the economy but about social justice.
"From the introduction of same sex marriage to taking people on low wages out of tax altogether, David Cameron has led a one nation government and it is in that spirit I also plan to lead."
Flanked by wife Samantha and their children as he delivered a parting speech outside Number 10 earlier, Mr Cameron said: "It's not been easy going and of course we have not got every decision right. But I do believe that today our country is much stronger," he said.
Mr Cameron thanked his family for keeping him "sane" during his time in office, and described Samantha as the "love of my life".
As the constitutional handover swung into effect, Mr Cameron went to see the Queen and formally told her he was quitting.
Mrs May then took her turn - entering as Home Secretary and emerging as the new PM.
Tory MPs hoping to win a place in Theresa May's first Cabinet showered their new leader with praise today, with one declaring: "We have our Angela Merkel".
Jeremy Hunt, the Health Secretary, compared Mrs May to the German Chancellor as he waits to find out if he will be promoted after spending three years with the tough health portfolio.
Mrs May is expected to make the most senior appointments of her Cabinet tonight.
But the skills minister Nick Boles has already resigned from the Government, jumping ship before Mrs May could sack him.
Mr Boles, who led Michael Gove's short-lived leadership campaign, was condemned for sending a text to supporters of Mrs May urging them to vote for the Justice Secretary to exclude Andrea Leadsom from getting through to the final two.
The cynical move backfired, with Mr Gove winning even fewer nominations from Tory MPs than the first round of voting.
Asked about his new boss today, Mr Hunt said of Mrs May: "I think around the cabinet table yesterday the feeling was that we have our Angela Merkel.
"We have an incredibly tough, shrewd, determined and principled person to lead those [Brexit] negotiations for Britain."
Delivering his valedictory comments before officially stepping down, Mr Cameron said: "When I first stood here in Downing Street on that evening in May 2010, I said we would confront our problems as a country and lead people through difficult decisions so that together we could reach better times.
"It's not been an easy journey and of course we have not got every decision right but I do believe today our country is much stronger.
"Above all it was about turning around the economy and with the 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.
"Politicians like to talk about policies but at the end it is about people's lives. I think of the people doing jobs who were previously unemployed. I think of the businesses that were just ideas in someone's head and that today are making a go of it and providing people with livelihoods."
Paying tribute to his family, the outgoing PM said: "I want to thank my children - Nancy, Elwen and Florence, for whom Downing Street has been a lovely home over this last six years. They sometimes kick the red boxes full of work. Florence - you once climbed into one before a foreign trip and said: 'Take me with you'.
Well, no more boxes. And above all I want to thank Samantha, the love of my life. You have kept me vaguely sane and as well as being an amazing wife, mother and businesswoman, you've done something every week in that building behind me to celebrate the best of voluntary service in our country."
Setting out what he sees as his legacy, Mr Cameron said: "I think of the hard working families paying lower taxes and getting higher wages because of the first ever national living wage.
"I think of the children who were languishing in the care system and who have now been adopted by loving families. I think of the parents now able to send their children to good and outstanding schools, including free schools that simply didn't exist before.
"I think of over 200,000 young people taking part in national citizens service, the first youth programme of its kind in the world, something again that wasn't there six years ago."
Mr Cameron said of Mrs May: "I will advise Her Majesty to invite Theresa May to form a new administration. I am delighted that for the second time in British history, the new Prime Minister will be a woman and once again a Conservative.
"I believe Theresa will provide strong and stable leadership in fulfilling the Conservative manifesto on which we were elected and I wish her well in negotiating the best possible terms for Britain's exit from the European Union."
On her final evening before entering No 10 as Prime Minister, Mrs May had dinner with the Chief Rabbi.
She and her husband Philip joined guests at the north London home of Ephraim Mirvis for the dinner, which had been arranged some time ago.
The Chief Rabbi said her decision to honour the engagement, following the fast-moving events which unexpectedly thrust her into Britain's top political job, was an indication of the esteem in which the new PM holds the UK's Jewish community.
Rabbi Mirvis described Mrs May as "a friend and champion of our community and of other faith".
The incoming PM had earlier in the evening been treated to a private tour of her new home in Downing Street by her current boss David Cameron.
Mr Cameron showed her the ropes of the luxury kitchen, which he spent £25,000 on a makeover when he arrived in 2010, in the plush flat above No 11 Downing Street, where the Cameron family live having swapped with Chancellor George Osborne's smaller family.
Mrs May, a keen cook, is expected to move in to the flat above No 11 with her husband and will be treated to the spacious kitchen, decked out with Nigella-standard units and surfaces.
Mr Cameron didn't take a last-opportunity to use the kitchen, however, instead treating his staff to a takeaway curry, spending more than £50 at his favourite Kennington Tandoori curry house.
The Chief Rabbi revealed Mrs May had dined with him on her last evening before becoming PM in a statement, in which he also paid tribute to outgoing PM David Cameron for his work to promote Holocaust remembrance and education.
In a statement, the Chief Rabbi thanked Mr Cameron for "his deep friendship and for his unwavering commitment to promoting the values of decency, respect, liberty and responsibility" and described him as "a man who not only speaks with great principle and conviction but who acts upon what he believes".
And he added: "Today, Theresa May becomes Prime Minister at a time of great political, social and economic uncertainty. Few people are more talented or better qualified to tackle these immense challenges.
"I recall the speed and the sensitivity with which she reached out to the Jewish community following the terror attacks on Jewish targets in Europe last year. As she made clear then, 'Without its Jews, Britain would not be Britain'.
"She has proved herself to be a friend and champion of our community and of other faith communities who share her values of tolerance and understanding.
"Last night, on the eve of her becoming Prime Minister, Theresa May kept a long-standing arrangement to join Valerie and me at our home for dinner.
"The fact that she did this in the midst of critically important preparations before taking up office is a reflection of her strong desire to keep to her commitments and the esteem in which she holds the British Jewish community.
"I was delighted to have the opportunity to give her my blessings at this very auspicious time.
"I wish her every success as Prime Minister and look forward to building upon our warm relationship over the coming years."
David Cameron treated his successor Theresa May to a private tour of his plush Downing Street flat last night as the incoming Prime Minister eyed up the Cameron family's luxury kitchen.
Mrs May, a keen cook, will be moving in to the flat above No 11, where Mr Cameron has lived with his family - with Chancellor George Osborne's smaller family living in the flat above No 10.
The incoming PM is expected to live in No 11, where the Camerons spent £25,000 to install a luxury new kitchen after arriving in 2010.
The Cameron family's kitchen is understood to be much better equipped and more spacious than their next door neighbours, with Nigella-standard units and surfaces.
But Mr Cameron didn't use the kitchen for one last time last night - instead he treated his staff by ordering one last curry as they frantically packed their bags to make way for the Mays.
Westminster's favourite curry house - Kennington Tandoori - tweeted a picture of their driver setting off with four big bags of curry to deliver their "last supper" to No 10.