In a touching moment, Charles put his hand around his wife, who appeared close to tears, after the couple shook every outstretched hand and acknowledged words of sympathy from the crowds during a 15-minute walkabout at the place gates.
There was an outpouring of support for the new monarch and his wife from well-wishers, with one calling out “God save the King” when the couple first arrived. Another shouting out “we love you King Charles and we loved your mum”, amid spontaneous cheering.
Charles was given a peck on the cheek by one female well-wisher and another clutched his hand and with both of hers and kissed it.
There was also an impromptu rendition of the national anthem from parts of the crowed, with the words changed to reflect the country now has a King, while another section shouted “hip, hip hooray”.
Many people held their phones aloft to try to catch a glimpse of them as they greeted members of the crowd and look at the tributes left for the Queen as the sun shone.
Colin Hennessy, 52, said: “It’s great to see the King.
“You can see he’s very emotional, but he was very grateful to everybody here.
“He thanked as many people as he could as he walked by.”
The King received the condolences ahead of his first meeting with new Prime Minister Liz Truss in the role of the UK’s monarch.
Charles had earlier been glimpsed for the first time since his accession to the throne as he departed Birkhall, his private home on the Balmoral estate, by car around 11:15am on Friday.
With Camilla, his new Queen Consort, in the front passenger seat, Charles sat in the back, dressed in his mourning clothes of a black suit and tie, looking sombre as he headed to Aberdeen Airport.
Camilla stared straight ahead as they were driven from the Scottish residence, where they had rushed to be at the Queen’s bedside when she fell gravely ill.
The couple stayed overnight at Balmoral, where Queen Elizabeth II died peacefully aged 96 on Thursday afternoon.
Members of the royal family had made the urgent dash to be with the frail monarch as her health failed.
Her children – Charles, the Princess Royal, the Duke of York and Earl of Wessex – travelled to the castle, as did the Duke of Cornwall and Cambridge, the Countess of Wessex and the Duke of Sussex.
Senior royals will have duties to perform in Scotland in coming days when the Queen’s coffin begins its journey back to the capital, but Harry was spotted leaving Balmoral on Friday morning.
The Sussexes, who were coming to the end of a whistle-stop visit to Europe when the Queen died, are expected to stay in the UK to attend the Queen’s state funeral, likely be held on September 19.
Tributes continue to be paid to the woman described by the Prime Minister as the “rock on which modern Britain was built”, with the Dalai Lama expressing his “deep sadness” over the death of the Queen in a letter to the King.
He told Charles: “Your mother lived a meaningful life with dignity, grace, a strong sense of service and a warm heart, qualities we all should treasure.”
The Queen’s former homes of Buckingham Palace, Windsor Castle and Balmoral continue to attract thousands of people wanting to pay their respects to the late monarch, with hundreds of bouquets, personal notes and candles being placed in her honour.
Charles has already turned his hand to his duties as monarch despite his grief.
He gave the order that a period of “Royal Mourning” for the Queen would be observed from now until seven days after her funeral.
Royal Mourning will be observed by members of the royal family, royal household staff and representatives of the royal Household on official duties, together with troops committed to ceremonial duties.
Royal salutes will be fired in London on Friday at 1pm in Hyde Park by the King’s Troop Royal Horse Artillery, and at the Tower of London by the Honourable Artillery Company, with one round being fired for each year of the Queen’s life.
Flags at royal residences were at half-mast on Thursday and will remain half-masted until 8am on the morning after the final day of royal mourning.
The King is expected to address the nation on television at 6pm on Friday, and hold his first audience with Prime Minister Liz Truss.
The PM and senior ministers will attend a public service of remembrance at St Paul’s in central London.