On Friday evening, the King - who travelled to London to meet with Prime Minister Liz Truss - made his statement to the public at 6pm (BST).
'We owe her the most heartfelt debt any family could owe to their mother for her love, affection, guidance, understanding and example,' he said of his mother.
'Queen Elizabeth was a life well lived, a promise of destiny kept and she's mourned most deeply in her party. That promise of lifelong service I renew to you all today.'
He spoke of the 'deep sense of gratitude' his mother served the people of so many nations, and later referred to the pledge she made during a broadcast from Cape Town in 1947, on her 21st birthday.
At the time, she promised to devote her life, whether it be short or long, to the service of her peoples. 'That was more than a promise, it was a profound personal commitment which defined her whole life,' he said of her service.
'Her dedication and devotion to sovereign never wavered,' he continued.
The new King referred to her 'abiding love of tradition' and 'fearless embrace', before highlighting the 'affection, admiration and respect she inspired became the hallmark of her reign' and her 'unerring ability to see the best in people'.
King Charles III continued: 'As the Queen herself did with such unswerving devotion, I too now solemnly pledge myself throughout the remaining time God grants me, to uphold the constitutional principles at the heart of our nation.
He added 'wherever you may live' and 'whatever may be your background or beliefs, I shall endeavour to serve you with loyalty, respect and love as I have throughout my life.
'My life will of course change as I take up my new responsibilities. It will no longer be possible for me to give so much of my time and energies to the charities and issues to which I care so deeply, but I know this important work will go on in the trusted hands of others.
He later addressed his family, starting with the Duchess of Cornwall: 'This is also a time of change for my family,' he began.
'I count on the loving help of my darling wife Camilla in recognition of her own loyal public service since our marriage 17 years ago.
'She becomes my Queen Consult. I know she will bring to the demands of her new role, the steadfast devotion to duty on which I have come to rely so much.
Later addressing Prince William and Kate Middleton, he said: 'As my heir William assumes the Scottish titles which have meant so much to me, he succeeds me as Duke of Cornwall and takes on the responsibilities for the Duchy of Cornwall which I have undertaken for more than five decades.
He added that his former title Prince Charles was one he'd 'been so privileged to bear'.
'With Catherine beside him our new Prince and Princess of Wales I know will continue to inspire and lead our national conversations, helping to bring the marshal to the centre ground where vital help can be given.'
The King turned his attention to Prince Harry and Meghan Markle, saying: 'I want also to express my love for Harry and Meghan as they continue to build their lives overseas.'
He concluded with a final tribute to his late mother: 'In a little over a weeks time we will come together as a nation, as a commonwealth and indeed a global community to lay my beloved mother to rest,' he said.
'In our sorrow let us remember and draw strength from the light of her example. On behalf of all my family I can only offer the most sincere and heartfelt thanks for your condolences and support. They mean more to me than I could ever possibly express.
'And to my darling mama as you begin your last great journey to join my dear late papa, I want simply to say this: thank you. Thank you for your love and devotion to our family and to the family of nations you have served so diligently all these years. May flights of angels sing thee to to thy rest.'
On Thursday, September 8 Her Majesty passed away, aged 96, in Balmoral, Scotland, surrounded by her family.
At around 1pm (BST) on Friday, a gun salute in London's Hyde Park took place, involving the firing of 96 rounds to mark each year of Her Majesty's life. A remembrance service that tied in with the King's speech was held at St Paul's at 6pm (BST), attended by the Prime Minister.
The service was open to the public, with 2,000 tickets released on a first-come-first-served basis, as reported by the BBC.
In order to receive a wristband, visitors were asked to visit the City of London tourism office on Carter Lane in London.
Charles will officially be proclaimed as King at the Accession Council at 10am (BST) on Saturday, September 10, Buckingham Palace has confirmed.
The council will be attended by several Privy Councillors and government ministers. Thereafter, the Principal Proclamation will be read at 11am (BST) from the balcony overlooking Friary Court at St James's Palace, central London, the BBC states.
In the last 24 hours, the King declared a period of Royal mourning, which will be observed for seven days after the funeral of his mother - making the total mourning period 17 days.
The date of the funeral is yet to be announced, but it's likely it'll take place in the next two weeks.
The Queen's coffin will lie at rest in Edinburgh, Scotland for 24 hours and will then be moved to Westminster Abbey to lie in state.
While there is no physical book for members of the public to write their condolences, one is invited to do so online here. Mourners have been asked to leave their flower tributes, if they so wish, in designated areas at Royal Residences.
You Might Also Like