Charles’s praise came as it emerged Prince George and Princess Charlotte will join their parents, the Prince and Princess of Wales, at the Queen’s state funeral, mourning their great-grandmother with more than 2,000 others at Westminster Abbey.
US President Joe Biden said the “world is better” because of the Queen as he offered his condolences to the British people for their loss, ahead of her funeral.
A minute’s silence was held at 8pm on Sunday, with Prime Minister Liz Truss standing outside Downing Street, as the nation paused to reflect on the eve of Queen’s burial.
In his message issued by Buckingham Palace, Charles said: “Over the last 10 days, my wife and I have been so deeply touched by the many messages of condolence and support we have received from this country and across the world.
“In London, Edinburgh, Hillsborough and Cardiff we were moved beyond measure by everyone who took the trouble to come and pay their respects to the lifelong service of my dear mother, the late Queen.
“As we all prepare to say our last farewell, I wanted simply to take this opportunity to say thank you to all those countless people who have been such a support and comfort to my family and myself in this time of grief.”
A previously unseen portrait of the Queen smiling with joy was released by the Palace on the eve of her funeral.
The image was taken by photographer Ranald Mackechnie ahead of the Platinum Jubilee celebrations, and shows the monarch beaming brightly at the camera in her Windsor Castle home.
The Duke of York was the last of the Queen’s children to pay tribute, with Andrew saying: “Mummy, your love for a son, your compassion, your care, your confidence, I will treasure forever.”
Andrew hailed the Queen for her “knowledge and wisdom infinite, with no boundary or containment”, adding: “I will miss your insights, advice and humour.”
Mr Biden visited Westminster Hall with first lady Jill Biden to pay his respects to the late monarch and after signing a book of condolence at Lancaster House said: “You were fortunate to have had her for 70 years, we all were.
“The world is better for her.”
The queue of people waiting to pay their respects to the Queen at her coffin in Westminster Hall ran through the capital with the expectation it would be closed at some point, ahead of the final mourner being able to view the coffin at 6.30am on Monday.
The Department for Culture, Media and Sport said the estimated wait was at least eight hours, down from 14 hours earlier in the day.
The King hosted a Buckingham Palace reception on Sunday for world leaders, welcoming around 500 global figures and their partners.
They included the US president and his wife, France’s President Emmanuel Macron and his wife, New Zealand Prime Minister Jacinda Ardern and her counterpart from Canada Justin Trudeau and Brazilian President Jair Bolsonaro.
The event was attended by William and Kate and other working members of the royal family including the Earl and Countess of Wessex, the Princess Royal and Vice Admiral Sir Tim Laurence, and the Queen Consort.
About 2,000 people including foreign royals, presidents and prime ministers will flock to Westminster Abbey on Monday for a day of pageantry, military processions and solemnity in honour of the Queen.
The Archbishop of Canterbury will give the sermon in front of a congregation including leading figures from UK national life.
Mourners in the capital will be treated to the spectacle of a ceremonial procession through the capital that will take the coffin – followed by her children and some of her grandchildren – to the state hearse at Wellington Arch.
It will travel to St George’s Chapel at Windsor Castle for a committal service attended by the Queen’s family, friends and personal staff before a private family burial service in the evening.