It has been a historic day for British politics, with Tony Blair leaving Downing Street after more than 10 years as prime minister.
He visited Buckingham Palace to resign at lunchtime, with Gordon Brown making the journey a few minutes later and leaving as the country's new leader.
As is traditional, the Queen invited him to form the next government - they spoke for 55 minutes.
Here are the main events as they unfolded throughout the day, with insight from BBC presenters and correspondents, as well as their guests.
1900 TO 2000 BST - BLAIR'S HOMECOMING
Tony Blair arrives at the Trimdon Labour Club to address some 500 Labour Party supporters.
Crowds have gathered outside the building, which is in the Sedgefield constituency he has represented for 24 years.
No longer prime minister, he has today announced he is standing down as the local MP to be a Middle East envoy.
Ministers will not face the traditional "walk of shame" or "walk of fame" in front of the media in Downing Street when Gordon Brown reshuffles the Cabinet, the BBC learns.
The new prime minister is understood to be likely to call and offer jobs on the telephone, or privately in person away from No 10.
Tony Blair travelled by train from London King's Cross to Darlington
It appears that the first anyone is likely to see of the new Cabinet is when they arrive for their first meeting, at a time yet to be confirmed.
Trimdon Labour Club is a "pretty humble" location for Tony Blair, compared to the other buildings he has seen today, the BBC's Mark Simpson in Sedgefield says.
"But he's going to have to get used to this. He is the local hero here, the local boy done good," he says as he awaits Mr Blair's speech.
"They call him Tony, they treat him like one of their own."
From Jersualem, BBC correspondent Matthew Price reports that there has been some local reaction to Mr Blair's appointment as a Middle East envoy.
An Israeli Foreign Ministry spokesperson describes being "delighted" about the move.
And an official working with Palestinian Authority President Mahmoud Abbas Mahmood Abbas says the appointment is "welcomed" and is sure that Mr Blair's commitment to peace in the Middle East is strong.
Mr Blair formally lets his local Labour Party know that he has stood down as their MP, Mark Simpson confirms.
He tells supporters it is good to be back where it all began for him, but stresses that all good things must come to an end.
And he admits that while it is one thing to be an absent MP as prime minister, it is quite another to do that as Middle East envoy.
"There was no way that he was going to be able to sort out the West Bank at the same time as sorting out planning complaints here in Trimdon," Mark Simpson adds.
1800 TO 1900 BST - FURTHER CHANGES
Tony Blair has arrived at Darlington railway station, on his way to address Labour Party supporters in the constituency he has represented since 1983.
Next month there is likely to be a by-election in Sedgefield, following Mr Blair's decision to stand down as a backbench MP to be a Middle East envoy.
The US Ambassador to the United Nations says he welcomes Mr Blair's appointment as an envoy.
It is a "very welcome development" given that Mr Blair is a very talented and gifted leader, Zalmay Khalilzad tells the BBC.
Mr Brown moved quickly to call world leaders after arriving at No 10
He says there was some debate among the members of the quartet - the United States, Russia, the United Nations and the European Union - about Mr Blair's terms of reference.
But he adds that in the end, the new envoy has a "very broad mandate", with a key task of developing Palestinian institutions.
BBC business editor Robert Peston understands that the Department of Trade and Industry will be "broken into two" by Mr Brown.
"What will remain of the old DTI will be a department focused on trade and deregulation," he tells BBC News 24.
A separate department will be created to emphasise Mr Brown's commitments to "improving the skills of British people" and "making Britain more competitive with training and skills", he adds.
Baroness Amos, the leader of the House of Lords, is to leave the Cabinet, BBC News 24's chief political correspondent, James Landale, learns.
She has accepted Mr Brown's nomination for her to be the UK's candidate for the post of EU Special Representative to the Africa Union, a job based in both Brussels and Addis Ababa.
1700 TO 1800 BST - BLAIR'S FUTURE CONFIRMED
Tony Blair is to be the special representative to the Mid-East quartet of the United States, Russia, the United Nations and the European Union, it is confirmed.
Representatives from the quartet had been meeting in Jerusalem to discuss the post of envoy.
New prime minister Gordon Brown has spoken to President George W Bush on the telephone, the White House says.
The US leader congratulated his opposite number and the two pledged to continue close cooperation, the AFP news agency reports.
Meanwhile French President Nicolas Sarkozy calls Mr Brown to congratulate him on his new job and says he wants them "to work very closely", according to Mr Sarkozy's spokesman.
They agreed to work on initiatives together, "notably on the issue of Darfur", and Mr Brown is also invited to Paris, David Martinon tells the Associated Press.
Health minister Andy Burnham refuses to be drawn on the departure of Patricia Hewitt as Health Secretary.
"We've had a day of great drama and of humour too. The rumour mill is now taking over," he tells BBC Radio 4's PM programme.
"There are precious few facts and I think we all need to relax a little bit and wait for the new prime minister to make some decisions."
Tony Blair has stepped down as the MP for Sedgefield, the Treasury's website confirms.
John Burton, Mr Blair's long-time election agent, says constituents will be "sad". "He's been their local MP. He's their friend," he tells BBC News 24.
There will now be a by-election, which is likely to be held on 19 July, Mr Burton adds.
"We want a local hard-working MP. We don't expect another Tony Blair. You don't get another Tony Blair. There's not many of them in the world."
The new prime minister's official spokesman confirms that Gordon Brown has spoken to Conservative leader David Cameron and Lib Dem leader Sir Menzies Campbell.
The conversation with Mr Cameron is described as "courteous and business-like".
Full details of the Cabinet reshuffle are likely on Friday lunchtime, adds the spokesman, who promises "regular" news conferences involving Mr Brown.
"Margaret Beckett has been informed by Gordon Brown that he does not wish her to stay in the post of foreign secretary," BBC political editor Nick Robinson reveals.
"She really wanted to stay," he tells BBC News 24.
But he believes she is a victim of her age - "Gordon Brown wants to reduce the average age of the Cabinet" - and her standing at the Foreign Office - "there have been some mutterings that she has not been up to the job".
Departing Health Secretary Patricia Hewitt hopes to carry on in the Cabinet, "but I believe that is unlikely", Nick Robinson says.
And James Landale then tells viewers: "We know that friends and colleagues attended a leaving party for Patricia Hewitt today."
1600 TO 1700 BST - PHONE CALLS & PROTESTS
Patricia Hewitt is to stand down as Health Secretary, sources tell BBC News 24's chief political correspondent, James Landale.
"That is the first of the movements that we are expecting - perhaps some a little later today, but mostly tomorrow - in the Cabinet reshuffle," presenter Matthew Amroliwala tells viewers.
Ireland's Taoiseach, Bertie Ahern, was one of the first leaders from other countries to talk to Mr Brown following his appointment.
"Mr Brown is a politician of exceptional experience and ability, and I am sure he will discharge the office of Prime Minister with distinction," he says.
There were protests by relatives of military personnel killed in Iraq
In their telephone call, they agreed that their two governments would continue to work closely together.
"In this new era in British-Irish relations, we have much to look forward to in developing our relationship in all its many dimensions. Of particular importance, of course, is to build on the precious foundation of peace in Northern Ireland," Mr Ahern adds.
Demonstrators have spent the day outside Downing Street, with many objecting to the presence of the British military in Iraq.
"I am very glad to see him go," Brian Stevenson of the protest coalition Stop the War says of Mr Blair.
"I am not sure there will be much of a change in foreign policy, but at least there is one murderer gone."
Meanwhile the principal speaker of the Green Party, Dr Derek Wall, asks: "Who would have thought that Blair would have been the best friend of George Bush, the US's most right-wing and least competent president in history?
"Who would have thought that Blair would have given us war after war, House of Lords sleaze, an accelerating climate-change crisis, and an outsourced, market-driven NHS?"
1500 TO 1600 BST - BROWN'S JOB BEGINS
Tony Blair poses for photographs with police protection officers at King's Cross station in north London.
Of course he is no longer prime minister, but now a backbench MP in Gordon Brown's governing Labour Party.
He allows more pictures before boarding the train to head to his constituency of Sedgefield in north-east England.
BBC political editor Nick Robinson says Mr Brown, the new prime minister, looked "hesitant and nervy as he got out of the car" on his arrival in Downing Street.
Mr Brown was "not sure where to stand" and when he gave a speech to the world's media, "his voice was croaky, cracking, even".
Gordon Brown talked of "a new government with new priorities"
He says: "He knew these words would be dwelt on and heard by millions of people."
Nick Robinson says Mr Brown is likely to be given a tour of No 10 first of all and then the phone calls will begin - to President George W Bush, to President Vladimir Putin, to the new French leader Nicolas Sarkozy.
Only then, will the new prime minister turn towards the task of choosing the next government, he says.
It is thought Mr Brown is being briefed on military matters, including the UK's nuclear weapons system.
1400 TO 1500 BST - A NEW PRIME MINISTER
As Gordon Brown meets the Queen, Hazel Blears - who is losing her job as Labour Party chairman - gives her predictions about the new prime minister's reign.
"I think he's a person very much committed to making sure that every single person in this country - whatever their background, their class, their race, their faith - has a chance to achieve their potential.
"That sense of ambition, of aspiration, of moving forward, will be very important," she tells BBC Radio Five Live.
And Tony Blair "is going to go on and do some great things across the world", she believes.
BBC political editor Nick Robinson says he expects Mr Brown to appoint Alistair Darling as chancellor before the day is out.
But this is likely to be the only new position made public on the new prime minister's first day, he adds.
In Mr Brown's constituency in Fife, "there is a sense of low-key pride", according to the BBC's Lorna Gordon, reporting from Kirkcaldy.
"They're immensely proud that a local boy has 'done good'. It was this area that made him the man, and indeed, the politician he is now."
There is "a small degree of disquiet", however, she adds.
"A couple of hours ago there was a protest of about 40 to 50 people from the Public and Commercial Services Union.
"They said if he wants to be a good prime minister, he'd better start listening to us now."
At Buckingham Palace, Mr Brown's Treasury car has been replaced with a heavily-armoured black Jaguar and six protection officers, BBC royal correspondent Nicholas Witchell says.
There is also a second security vehicle waiting for the new prime minister when he leaves the palace.
Nick Robinson tells BBC News 24 that the immediate increase in security marks "the beginning of a huge change" for Mr Brown.
"It is a shock to politicians - there are things they think they can do and they can't. It will be a huge change in his life and one that I don't imagine, like anybody else, he'll enjoy."
Liberal Democrat leader Sir Menzies Campbell describes Mr Blair's final prime minister's question time as a rather "flat affair".
"People were concerned to give him a good send-off, rather than to challenge him," he tells BBC News 24.
There was also no mention of Quentin Davies, the Conservative MP who defected to Labour on Tuesday, Sir Menzies points out.
This is "a new era" of politics, he adds, refusing to be drawn on questions about Mr Brown's approaches to senior Liberal Democrats as he tried to recruit them to his first Cabinet.
The Browns leave the palace at 1448 BST. It is official - Britain has a new prime minister.
Mr Brown spent 55 minutes with the Queen, Nicholas Witchell is told. "They seem to be firm friends and allies already," the correspondent jokes. "They didn't seem to want to leave each other's company."
Back in Downing Street, Mr Brown gives his first public speech as prime minister.
"I want the best of chances for everyone. That is my mission.
"If we can fulfil the potential and realise the talents of everyone then I am absolutely sure that Britain can be the great success story of this century."
He promises "a new government with new priorities", saying that he will "continue to listen and learn" and acknowledging that he has "heard the need for change".
"There is no weakness in Britain today that cannot be overcome by the strength of the British people," he adds, before concluding: "Now let the work of change begin."
1300 TO 1400 BST - FOND FAREWELL
Tony Blair wraps things up at No 10, with an emotional farewell to staff where "people will line the corridor", says news presenter Huw Edwards in Downing Street.
The prime minister then poses for photographs outside with wife Cherie and his children - sons Euan, Nicky and Leo and daughter Kathryn.
The children go back inside through the famous black door, while Mr Blair leaves for Buckingham Palace with his wife.
Mrs Blair waves to the media as she gets into the prime ministerial limousine.
The Blairs' possessions have been removed from their home
She laughs as she says: "Goodbye - I don't think we'll miss you."
Within three minutes, at 1312 BST, the couple arrive at Buckingham Palace.
They are greeted by the Queen's senior lady-in-waiting and an equerry. This is the last time that Mr Blair will be seen in public as the prime minister.
For a few minutes, the UK is without a prime minister, as Mr Blair completes his final audience with the Queen as prime minister.
BBC political editor Nick Robinson says that the gap between the handover is a fraction of what it once was.
When David Lloyd George resigned in 1922, it was four days before his replacement, Andrew Bonar Law, took the reins - now, it takes only a matter of minutes.
And what will Gordon Brown be thinking of? "I think he'd be thinking, 'My God, I've actually got it.'"
He calls Mr Brown "the longest-serving 'next prime minister' - it's very hard to stay the apprentice for that long", he says.
Staff at the Treasury are gathering by the building's security turnstiles, waiting to greet Gordon Brown.
"He'll be leaving from here in his official Treasury car - it's here with the engine running outside ready to whisk him off," says BBC political correspondent Carole Walker.
The Blairs leave the palace at 1340 BST.
"Only a matter of minutes pass before we see the next man, Gordon Brown, making his way here," explains BBC royal correspondent Nicholas Witchell at Buckingham Palace.
There are cheers at the Treasury - staff have gathered in an atrium, peering over the banisters and applauding Mr Brown as he departs as chancellor.
Mr Brown spent about 55 minutes with the Queen at the palace
"Waiting outside the Treasury, there are crowds - five or six deep - giving him a big round of applause, shouting their best wishes," Carole Walker adds.
Mr Brown arrives at the palace, with his wife Sarah, at 1351 BST.
1200 TO 1300 BST - PRIME MINISTER'S QUESTIONS
BBC political editor Nick Robinson says he has "no doubt" that Mr Blair will be feeling nervous ahead of his final appearance at prime minister's questions.
"Any great performer - and whether you love him or loathe him he is one of the truly great political performers - gets nervous before an occasion like this," he writes in his blog.
"He knows the clips from this will be shown not just on tonight's news, but endlessly as part of the archive of the Blair years. He'll want to enjoy it, and to get it right."
Tony Blair's wife and children arrive at the public gallery in the Commons to watch the proceedings.
Mr Blair begins the session by paying tribute to British military personnel. "They are the bravest and the best," he says.
Then there is an exchange of pleasantries between Mr Blair and the leaders of the Conservative Party and the Liberal Democrats.
For the Tories, David Cameron says: "We wish him and his family well, and we wish him every success in whatever he does in the future."
Mr Blair joked with MPs that he had already received his P45 form
The prime minister returns the compliment, saying Mr Cameron was "most proper, correct and most courteous in his dealings with me".
Lib Dem leader Sir Menzies Campbell says that despite their political disagreements, particularly over Iraq, Mr Blair has been "unfailingly courteous" and extends his best wishes.
Again, Mr Blair praises his opposite number, hailing particularly the "generosity of spirit" he has seen in Sir Menzies.
There is a lighter moment as Mr Blair says he has received his P45, the document which employees are given as they depart any job.
And when listing his engagements, as is traditional at prime minister's questions, he reports having had meetings with ministerial colleagues this morning.
"I will have no such further meetings today - or any other day," he adds, to a great roar of laughter from MPs.
Mr Blair receives a standing ovation as the half-hour session ends - it is extremely rare to hear applause in Parliament.
Tony Blair received a standing ovation as he left the Commons
"I've never seen anything like that," Five Live's chief political correspondent John Pienaar says. "It was a genuinely emotional moment."
When it is all over, Nick Robinson tells BBC News 24 that he thinks it was not the farewell that Mr Blair would have expected.
Mr Cameron "sucked all the political heat" out of the occasion by asking about the floods in northern England - and wishing Mr Blair and his family the best, he says.
And the prime minister was denied a final opportunity to swipe the opposition, he adds. "This was more a sentimental farewell than a long-waited-for political bashing."
1100 TO 1200 BST - LENSES & LIMOUSINES
BBC News 24's Matthew Amroliwala says Downing Street is rammed full of press and camera crews.
The world's media have descended on No 10 to mark the end of Mr Blair's 10 years in power.
The prime minister strides out to his waiting limousine, pausing only briefly to acknowledge a baying crowd of reporters and photographers, before being driven out of Downing Street to his office.
A media scrum looked on as Mr Blair left Downing Street
Mr Blair's final prime minister's questions, at 1200 BST, will be "a special occasion", according to Five Live's chief political correspondent, John Pienaar.
"We know that Tony Blair is at least 25% perfect thespian and he's going to enjoy the stage that he's on. The House will conspire to make it a theatrical occasion.
"The manners of the House dictate that [Conservative leader] David Cameron will wave goodbye in a similarly good-humoured fashion."
"For the 10th time in her reign, the Queen will witness the resignation of her prime minister," says BBC royal correspondent Peter Hunt, looking ahead to this lunchtime.
But he adds that little will emerge about the precise conversation between Mr Blair and the Queen.
"He and she will be the only people in that room - apart from her corgis. The prime ministers never leak about what's going on and neither does she."
Mr Brown's unofficial biographer, Tom Bower, tells BBC News 24 what the electorate should expect from the incoming prime minister.
He describes Mr Brown as a "principled" man, shaped by his father's moral compass, and a "socialist, who believes in the state".
But he also says Mr Brown is controlling and does not like criticism or challenges; he relies on a cabal of insiders with similar views and is determined to create a "Brown Era".
The BBC's chief political correspondent James Landale says he bumped into Mr Blair earlier after a Lobby briefing.
For probably the last time in his career, he was able to greet Mr Blair with: "Good morning, Prime Minister."
1000 TO 1100 BST - REMOVALS & RESHUFFLES
The Blair family's possessions are being loaded into a white lorry parked outside 10 Downing Street.
"It's a vaguely humiliating scene, in a sense, the departure of a prime minister," says Jon Sopel, presenter of BBC One's The Politics Show.
"There is no privacy to it. You see the possessions being taken out by the removal men, loaded into the back of the trucks.
"I remember this from 17 years ago when Margaret Thatcher's removal men came in after she had been brutally brought down."
We may know who is to take over from Gordon Brown as chancellor today, sources tell the BBC.
But it is understood that major announcements on the forthcoming Cabinet reshuffle are likely to be held back until Thursday at the earliest.
Immigration Minister Liam Byrne predicts Mr Brown's reign will be "a blend of continuity and change which is a difficult balancing act to strike in politics".
He says Mr Brown's focus would be on bringing more power to local communities and "less fixation on the media".