King Charles III was heard telling well-wishers he "dreaded this day" as he greeted the crowds outside Buckingham palace. Queen Elizabeth died surrounded by her family at Balmoral on Thursday - and the new King stayed overnight in the Scottish Highlands before returning to London earlier today as a period of national mourning begins.
Charles was supported by wife Camilla, who will now be known as Queen Consort, a title which was Elizabeth II's "sincere wish" that she should receive. Onlookers shouted three cheers for Charles as one woman leaned over to kiss him on the hand - and he thanked them for their support while giving a rare show of his emotions.
For the latest updates as the world mourns the Queen and King Charles III's reign begins, follow our live blog.
During his 15-minute walkabout, the King was heard telling well-wishers: "Thank you so much, it's so kind, it really is."
He also said "'God bless you" and 'I've really dreaded this day" as huge crowds began chantng "God save the King".
One woman shouted to him: "We love you King Charles and we loved your mum."
Huge crowds cheered on the new monarch, who shook hands with a large number of members of the public who had been waiting patiently for hours.
One woman even gave him a kiss on the hand as he greeted those who had gathered outside Buckingham Palace - and a bugle sounded as he made his way through the main entrance.
Earlier today, the King and Queen were seen leaving the royal family's Scottish Highlands estate to make their way back to London.
He sat in the back seat of the chauffer-driven car, with Camilla in the front seat, for the drive to Aberdeen airport.
Judi told The Mirror: "While his youngest son left Balmoral alone to fly back to his wife Charles sat in his car behind Camilla, looking almost as though he needed to be isolated and silent in his grief at the present time.
"His facial expression bore some signs of shock, which can be normal, even after an expected death.
"He sits slightly hunched and diminished and with his steepled brows and his cheeks and mouth pulled back slightly at the corners his eye expression suggested tearfulness."
King Charles was at Balmoral for his mother's final hours along with his brothers, Princes Edward and Andrew, and their sister, Princess Anne.
In a statement, Charles said: "The death of my beloved Mother, Her Majesty The Queen, is a moment of the greatest sadness for me and all members of my family.
"We mourn profoundly the passing of a cherished Sovereign and a much-loved Mother. I know her loss will be deeply felt throughout the country, the Realms and the Commonwealth, and by countless people around the world.
"During this period of mourning and change, my family and I will be comforted and sustained by our knowledge of the respect and deep affection in which The Queen was so widely held."
The King, who was the nation's longest-serving heir apparent, having been in that role since he was three, is now fulfilling his royal destiny as monarch.
The public will notice many changes in the coming months and years, as stamps and coins with King Charles' face will be put into circulation.
* This weekend, the Daily Mirror and Sunday Mirror celebrate the life of Her Majesty the Queen with a commemorative special filled with all the key moments from Britain’s longest reigning monarch. Be sure to pick up your copy of the Daily Mirror and Sunday Mirror to get poth pullouts.
You can leave your tributes to Queen Elizabeth II here
