Boris Johnson carried out a brutal cull of Theresa May's ministers as he formed a new Government dedicated to his goal of delivering Brexit.
In his first speech as Prime Minister, he promised to give the country "the leadership it deserves" and said he would meet the October 31 Brexit deadline – "no ifs or buts".
The first appointments to Mr Johnson's new Cabinet were Sajid Javid as Chancellor and Priti Patel as Home Secretary.
Dominic Raab is also expected to return to the Government.
Philip Hammond - resigned as chancellor in the last hours of Mrs May's premiership
Jeremy Hunt - Boris Johnson's former leadership rival announced he was returning to the backbenches after serving as foreign secretary
Penny Mordaunt - departs after a brief spell as defence secretary
Rory Stewart - leaves the international development department after already saying he would not serve under Mr Johnson
David Gauke - the ex-justice secretary made no secret of his disagreements with Mr Johnson
Damian Hinds - leaves the Department for Education
Chris Grayling - departs after a much-criticised spell as transport secretary
David Lidington - had been Mrs May's de facto deputy
James Brokenshire - the close ally of Mrs May had served most recently as housing secretary
Liam Fox - the Brexiteer has been removed as international trade secretary
David Mundell- the ex-Scottish secretary said he was not surprised to return to the backbenches
Karen Bradley - removed as Northern Ireland secretary
Greg Clark - his departure as business secretary was widely anticipated
Mel Stride - returning to the backbenches after the briefest of spells as Commons leader
Jeremy Wright - the culture secretary has also departed
Sajid Javid - Chancellor
Priti Patel - Home Secretary
The appointments came after Mr Johnson wielded the axe, with more than half of Mrs May's Cabinet either quitting or being sacked.
Jeremy Hunt, Mr Johnson's rival in the Tory leadership race, left the Government after refusing to be demoted from foreign secretary.
Penny Mordaunt and Liam Fox, prominent backers of Mr Hunt, were among the first to be sacked as Mr Johnson carried out a radical reshaping of the Cabinet.
Other ministers shown the exit include Damian Hinds, Greg Clark, David Mundell, Karen Bradley, James Brokenshire and Mel Stride.
Before Mr Johnson even took office, Philip Hammond quit as chancellor, David Gauke resigned as justice secretary and Rory Stewart left his post as international development secretary.
David Lidington, Mrs May's de facto deputy prime minister, left office at the same time as his boss while Chris Grayling resigned as transport secretary.
Mr Johnson's first dramatic hours as Prime Minister began with a wide-ranging speech in Downing Street shortly after being asked to form a Government by the Queen.
Watched by girlfriend Carrie Symonds, Mr Johnson promised he would "change this country for the better" and vowed to prove the Brexit doubters wrong.
He said: "I am standing before you today, to tell you the British people, that those critics are wrong – the doubters, the doomsters, the gloomsters are going to get it wrong again."
He predicted that "the people who bet against Britain are going to lose their shirts because we are going to restore trust in our democracy".
He added: "And we are going to fulfil the repeated promises of Parliament to the people and come out of the EU on October 31, no ifs or buts.
"And we will do a new deal, a better deal that will maximise the opportunities of Brexit while allowing us to develop a new and exciting partnership with the rest of Europe based on free trade and mutual support.
"I have every confidence that in 99 days' time we will have cracked it."
He promised action to fix the social care crisis, make the streets safe and improve the NHS.
He said: "I will take personal responsibility for the change I want to see.
"Never mind the backstop, the buck stops here."
On the issue of the Irish border – the main stumbling block in reaching a Brexit deal – Mr Johnson said he is "convinced" a solution could be found without checks at the border and without "that anti-democratic backstop".
But he added: "It is of course vital at the same time that we prepare for the remote possibility that Brussels refuses any further to negotiate and we are forced to come out with no deal."
Mrs May had earlier used her farewell address in Downing Street to urge Mr Johnson to secure a Brexit deal.
She said the "immediate priority" was "to complete our exit from the European Union in a way that works for the whole United Kingdom".
The handover of power came on a dramatic day at Westminster which also saw:
– Greenpeace protesters attempt to block Mr Johnson's car on its way to Buckingham Palace.
– European Council president Donald Tusk call for Mr Johnson to set out a detailed plan for Brexit.
– Mr Johnson appoint controversial Vote Leave mastermind Dominic Cummings in an advisory role.
In his Downing Street address, Mr Johnson was keen to set out a domestic agenda in order to ensure his term in office is not defined by Brexit.
He confirmed his campaign pledge to put another 20,000 police on the streets, he said work would start this week on 20 new hospital upgrades, and he promised to "fix the crisis in social care once and for all" with a plan to give every older person "the dignity and security they deserve".
Acknowledging the divisions in the country, Mr Johnson said he would answer the pleas of the "forgotten people and the left behind towns", with investment in new transport links and infrastructure.
He also hailed the "awesome foursome" of the four nations of the UK – England, Scotland, Wales and Northern Ireland – "who together are so much more than the sum of their parts".
Mr Johnson faces a difficult task as he attempts to govern with a majority of just two and now a host of disaffected former ministers.
His answer appears to be reuniting many of the key players from the Vote Leave referendum campaign which secured victory for Brexit in 2016.
Ms Patel was a leading player in the campaign and returns to government after she was forced by Mrs May to resign as international development secretary over unauthorised contacts with Israeli officials.
Mr Cummings clashed with officials and politicians while he was an adviser to Michael Gove in the coalition government, but Mr Johnson clearly believes his forthright style will help steer Brexit through.
The appointment of the abrasive Vote Leave campaign director is controversial given that earlier this year he was found to be in contempt of Parliament for refusing to give evidence to a committee of MPs investigating "fake news".