King Charles III and Queen Consort Camilla have welcomed royalty and leaders from across the globe at a Buckingham Palace for a special reception ahead of the Queen's state funeral.
The new monarch greeted scores of foreign dignitaries, including the US President Joe Biden and his wife, Jill, who paid tribute at the coffin of Queen Elizabeth II on Sunday afternoon at Westminster Hall.
The President skipped the queues and paid his respects as he looked down from a balcony at around 5pm.
He later told reporters the Queen reminded him of his own mother.
Speaking at Lancaster House, he was asked why he drew the comparison, and said: "She had that look like, 'are you OK? Anything I can do for you? What do you need?'
"And also 'make sure you do what you're supposed to do'," he joked, wagging his finger.
He added: "I have talked about how my mother and father thought that everyone, no matter who they were, no matter what their station, no matter where they are from, deserved to be treated with dignity.
"And that's exactly what she communicated - just the way she walked by her staff, just the way she acted.
"I think what she gave was a sense of, above all, the notion of service - we all owe something.
"There is something in our capacity to do that can make not just the world better, but your neighbourhood better, your household better, your workplace better, and that's what she communicated to me and it was an honour to meet her."
The French President Emmanuel Macron and his wife Bridgette, earlier gifted King Charles a book of pictures celebrating his mother's visits to France during her 70 year reign.
Others expected to attend the funeral include the Japanese Empress Masako and Emperor Naruhito, who met Her Majesty while studying at Oxford in the 1980s, and King Felipe of Spain and his wife, Queen Letizia.
The European Commission President Ursula von der Leyen, Italian President Sergio Mattarella, the President of Germany Frank-Walter Steinmeier will also attend.
Liz Truss, who was invited to form a government by the late Queen less than a fortnight ago, held a second private audience with the King on Sunday morning before attending the Buckingham Palace reception.
President Biden and the First Lady arrived in the presidential car known as The Beast in the middle of a convoy of vehicles at the back of the palace shortly before 6pm.
Members of the president's entourage mingled with household staff and police next to the palace lawn while the reception took place inside.
They were met by Foreign Secretary James Cleverly and Robert Alexander, head of government hospitality at the Foreign Office as they recalled fond memories of Her Majesty.
President Biden told them he remembered when the Queen invited him and the first lady over for tea and - as he joked - "crimpets", which "she kept offering me more and I kept eating everything she put in front of me".
Up to 500 dignitaries from around the world are expected to descend on London to attend the first state funeral since the wartime prime minister Sir Winston Churchill's service in January 1965.
More than 400 Foreign, Commonwealth and Development Office volunteers have helped coordinate the massive challenge of receiving royalty and world leaders, with just 10 days' notice - the equivalent of hundreds of state visits.
In order to arrange the logistical nightmare, officials had given advice to dignitaries to travel in Government provided buses to the funeral service from an undisclosed location, rather than using private vehicles.
At least 10 coaches arrived filled with guests, who solemnly walked into the palace.
Some leaders were seen greeting each other while others remained silent as they walked up the steps.
Most of the guests were all dressed in black, while some were seen wearing traditional clothing native to their countries.
The advice prompted concern in some quarters, but New Zealand's Prime Minister Jacinda Arden said on Sunday: "I'm interested there's so much fuss about it, I don't think the bus warrants too much fuss. This just makes good sense."
A core team of around 100 officials are also staffing a central operational response team co-ordinated by the Cabinet Office tasked with delivering the biggest public service operation since the Olympics.
A daily ministerial meeting is chaired by Nadhim Zahawi in his role as Chancellor of the Duchy of Lancaster, with the National Situation Centre constantly providing updated information to cabinet members.
Additionally the Department of Culture Media and Sport (DCMS) has dispatched around 300 civil service martials to support the Queen's lying-in-state - with duties including handing out tissues for those overcome by emotion.
The Bidens were among thousands of members of the public who paid tribute at the coffin on Sunday.
Following the Queen's death on September 8, the US President said "her legacy will loom large in the pages of British history, and in the story of our world".
“In a world of constant change, she was a steadying presence and a source of comfort and pride for generations of Britons, including many who have never known their country without her,” he said in a statement released by the White House.
On Saturday, the leaders of Australia, Canada, and New Zealand also stood in silence as they paid respects to the late monarch in Westminster Hall - the oldest building in the Palace of Westminster.
Speaking to the BBC's Sunday with Laura Kuenssberg programme, Sir Tony Radakin, the Chief Of the Defence Staff, said more than 10,000 military staff are also due to perform their "last duty" to the Queen at the state funeral.
He said military chiefs have been told to "up their game" and listen to a metronome at 75 beats per minute in order to get the right rhythm for the funeral procession.
"For all of us, this is our last duty for Her Majesty the Queen and it's our first prominent duty for His Majesty King Charles, and we're representing the nation, we're representing our mothers, our grandmothers, our fathers, our friends, and everybody's very, very aware of that."
He added: "We have the plans and now we have to execute them and there's lots of brilliant people that are enabling that and it's coming together as well.
"So the army, the Royal Navy, the Air Force, but also our civil servants, and we're helping other people in London, the emergency services, some of the volunteers as well, and so that this is a sombre occasion, but it's done with the utmost respect and also affection."
Pressed on whether he was nervous ahead of the service at Westminster Abbey, he replied: "There's always an element of apprehension, but we have brilliant people that help at every level, some generals that have been planning this for a long time.
"We have warrant officers and non-commissioned officers that look at the precise execution, and that's at my level and then all the way down."
