Charles III has this morning (Saturday) been proclaimed King and Head of the Commonwealth after a historical Accession ceremony.
During his declaration, the King vowed to follow his mother's "inspiring example".
The Principal Proclamation was read in public for the first time by the Garter King of Arms from the balcony overlooking Friary Court at St James's.
Crowds gathered outside to watch the momentous occasion, hearing a rendition of God Save The King and three cheers being given to the new monarch.
Gun salutes subsequently took place to mark the proclamation.
During his declaration, King Charles III said:
"It is my most sorrowful duty to announce to you the death of my beloved mother, the Queen," he says. "I know how deeply you, the entire nation, and I think I may say the whole world, sympathise with me in the irreparable loss we all suffered.
"It is the greatest consolation to me to know of the sympathy expressed by so many to my sister and brothers, and that such overwhelming affection and support should be extended to our whole family."
"To all of us as a family as to this kingdom, and the wider family of nations of which it is a part, my mother gave an example of lifelong love and of selfless service.
"My mother's reign was unequalled in its duration, its dedication and its devotion.
"Even as we grieve, we give thanks for this most faithful life."
He says he will dedicate "what remains of my life" to his new role.
In his declaration, King Charles continued:
"In taking up these responsibilities, I shall strive to follow the inspiring example I have been set in upholding constitutional government and to seek the peace, harmony and prosperity of the peoples of these islands, and of the Commonwealth realms and territories throughout the world.
"In this purpose, I know that I shall be upheld by the affection and loyalty of the peoples whose Sovereign I have been called upon to be, and that in the discharge of these duties I will be guided by the counsel of their elected parliaments."
King Charles III is now signing two copies to confirm the oath has been taken, before Prince William and the Queen Consort, Camilla, sign as witnesses.
The ceremony opened with the announcement of the death of Queen Elizabeth II, after which King Charles III was formally announced as the nation's new sovereign.
King Charles also announced the day of the Queen's Funeral will be a bank holiday.
The sad event is expected to be held on Monday, September 19.