London(CNN) King Charles III dedicated "what remains to me of my life" to "the heavy task that has been laid upon me" after he was formally confirmed as the new king of the United Kingdom in a ceremony steeped in tradition and pageantry at St. James's Palace on Saturday.
Charles became monarch on the death of Queen Elizabeth II on Thursday, but Saturday's event officially confirmed the transition of power.
The King paid tribute to his mother before the gathered Accession Council, saying his mother "gave an example of lifelong love and of selfless service."
"Her reign was unequaled in its duration, its dedication and its devotion. Even as we grieve, we give thanks for this most faithful life," he said during the historic ceremony, which was televised for the first time.
The ancient ceremony at the 500-year-old St. James's Palace in London consists of two parts. In the first part, the sovereign's death was formally announced and the new sovereign proclaimed. It was a closed meeting, without King Charles III, attended by dignitaries and members of the Privy Council, which is a panel of royal advisers.
British Prime Minister Liz Truss was joined at the event by several of her predecessors in the role, including Boris Johnson, Theresa May, David Cameron and Gordon Brown.
Charles was officially proclaimed "King, head of the Commonwealth, defender of the faith" by the Clerk of the Privy Council Richard Tilbrook, who then declared "God Save the King," which was repeated by the crowd in the packed room.
The proclamation confirming Charles as King was then signed by his son William, the new Prince of Wales, and Charles' wife Camilla, the Queen Consort -- both of whom are members of the Privy Council. It was also signed by council members Lord President of the Council Penny Mordaunt, Truss and the Archbishop of Canterbury Justin Welby.
The second part of the Accession Council was attended by the King.
King Charles also approved orders declaring the day of Queen Elizabeth's State Funeral as a bank holiday in the United Kingdom, though the date of the funeral is yet to be announced.
Outside the palace, in Friary Court, trumpeters played along with a military display, while a gun salute echoed across the capital from the Tower of London and in Hyde Park following the ceremony. A second proclamation took place an hour later in the heart of the financial district of the City of London, the Royal Exchange.
Members of Parliament took their oath of allegiance to King Charles III in the House of Commons on Saturday afternoon.
King Charles III was expected to hold audiences in Buckingham Palace with religious leaders and political leaders on Saturday afternoon, according to a palace statement.
The King was to meet the Archbishop of Canterbury and the Dean of Westminster, Buckingham Palace said. He was also to receive the Prime Minister and Members of the Cabinet, as well as leaders of opposition political parties.
Back at Balmoral, members of the Royal Family -- dressed in black -- waved goodbye to well-wishers at the gates of the royal estate on Saturday afternoon, following their return from a private church service.
Prince Andrew, the Duke of York and the late Queen's second-born son, shared an embrace with his daughter Princess Eugenie as she shed a tear after a walkabout with the public.
Andrew thanked members of the public for coming, as the Royal Family was greeted by people waving, applauding, and laying floral tributes in honor of the Queen.
"We've been allowed one day, now we start the process of handing her on," he said, according to PA Media.