"She would never have believed all this," Prince William told wellwishers of his grandmother. "It seems to be uniting everyone and bringing everyone together." Photo / Getty Images
The late Queen would "never have believed" the sight of the queue to see her lying in state, the Prince of Wales said as he praised the unity and new friendships forged through mutual grief.
The Prince, who joined his father for a walkabout with members of the public queuing in Lambeth, said seeing the number of people wanting to pay their respects was "quite emotional".
"She would never have believed all this," he told well wishers of his grandmother. "It seems to be uniting everyone and bringing everyone together."
Saying he hoped people were making "friends for life" while waiting in line, where they had been moving almost constantly for 12 hours at that point, he shook hundreds of hands and repeatedly told people he hoped they were not too cold and tired.
"It means an awful lot that you're here, it really does," he said. "You're doing an amazing job.
"People have queued for miles and miles, it means so much to our family. It's like nothing we could have imagined".
The King, speaking to a 69-year-old NHS worker, told her: "It's worth it when you get there - she [the late Queen] would have been very touched by all this."
Prince William made a surprise appearance alongside his father the King near Lambeth Bridge in a boost to the morale of people who joined the queue in the middle of the night to see the Queen's coffin.
"When you get in there, it's very emotional," he told them. "I hope the queue moves quickly. You're nearly there.
"I can't believe the scale of this queue and there are people from everywhere."
One woman asked him to make sure the Queen's corgis are well looked following her death.
"I saw them the other day," the Prince replied. "That made me a little bit sad, but they're going to be well looked after. They're two very sweet corgis."
Another showed him a large soft toy Paddington Bear and joked she and her family had brought it with them from Peru.
It is the first time since the death of Queen Elizabeth II that the pair have undertaken a joint engagement in a sign of their now-close working relationship as king and heir.
Later on Saturday the Prince and Princess of Wales joined the King for lunch at Buckingham Palace, where he hosted governors-general from the Commonwealth Realms.
In a signal of the Wales' increasingly central role in overseas diplomacy, they joined a close-knit group of a dozen governors-general for conversation about the late Queen and the Commonwealth she held so dear.
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At Buckingham Palace, the couple joined extended members of the senior working Royal family for a reception, along with the Queen Consort, Princess Royal and Sir Timothy Laurence, and the Earl and Countess of Wessex.
The Princess of Wales, wearing a black dress and a three-strand pearl necklace, was seen conversing with Commonwealth dignitaries, at one point placing her hand on the arm of Saint Lucia governor-general Cyril Errol Melchiades Charles.
The Princess's three-strand pearl necklace and pearl earrings were both gifts from the late Queen.
The Princess was photographed deep in friendly conversation with the Queen Consort, as the Royal family mingled with the governors-general of Antigua and Barbuda, Australia, the Bahamas, Belize, Canada, Grenada, New Zealand, Papua New Guinea, Saint Lucia, Saint Vincent and the Grenadines, the Solomon Islands and Tuvalu.
Members of the Royal family - the then-Duke and Duchess of Cambridge and the Earl and Countess of Wessex - have this year been on tours to the Caribbean, which were overshadowed by the series of declarations that islands would soon seek to remove the Queen as head of state.
The palace has emphasised that the decision would be a matter for the people of each country. The new King has succeeded his mother as Head of the Commonwealth and is keen to continue her work in keeping the "family of nations" together.
Earlier in the day, the King had invited the Prince of Wales to meet him at the end of a visit to the Metropolitan Police Service Special Operations Room, the headquarters of police plans for public safety in the aftermath of the Queen's death under Operation London Bridge.
The King's visit was designed at his personal request to thank servicemen and women, including members of the British Transport Police, London Ambulance Service, the Army and London Fire Brigade.
He was greeted on arrival by new Met Police Commissioner Sir Mark Rowley, Home Secretary Suella Braverman, Mayor of London Sadiq Khan and Lord Lieutenant of Greater London Sir Ken Olisa.
Speaking to the operation planning team, who also prepare the policing efforts at football matches and protests in the capital, the King asked: "Have you been planning for a long time… or have you just been drafted in?"
One officer responded: "Yes your Majesty, we've been planning for about three years. There were teams before us."
He replied: "And the plans are working?"
The officer said: "They are, absolutely."
"That's the most encouraging thing," the King said, describing their work as "absolutely fantastic" and adding: "Thank you."
Outside, father and son walked down a long line of well wishers first, to ringing shouts of "God Save the King" and "three cheers".
Several members of the public told the King they were praying for him and his family.
The Prince, left well behind, joked that his father was the more professional hand-shaker, saying he could teach him some tricks on how to do walkabouts.
"He's got the quickest hands ever," he said, laughing. "I've got to pick up some tips".
"How are the fingers and toes?" he asked those who had waited through the night in hats and gloves, reassuring them: "When we go, you'll be able to move a bit faster! I'm conscious I'm holding you up."
He made sure to ask small children in the line whether they were being well looked after, and if they had snacks or "sweeties" to keep them going.
Hearing the variety of countries people had travelled from, including the United States, the Czech Republic, Spain and Canada, he said: "You will make friends for life here, doing this."
One mourner was heard telling the King: 'I am from the Netherlands!' to which he replied: "Wow, my mother would have been very touched."
Rachel Burridge, 55, a travel agent from Bishop's Stortford, told him: "I'm so sorry about your mother."
"We were very lucky to have her," the King said, before Ms Burridge replied: "Yes, and now we're lucky to have you."