King Charles III gave his son William his old title, Prince of Wales, as he gave his first address as the new monarch on Friday evening.
The 73-year-old became King following the death of his mother, Queen Elizabeth II, on Thursday at the age of 96.
In his first televised speech as the King, Charles formally declared that his son and heir will now be known as the Prince of Wales, while William's wife Catherine will be the new Princess of Wales, a title formerly held by William's late mother Princess Diana.
"As my heir, William now assumes the Scottish titles which have meant so much to me. He succeeds me as Duke of Cornwall and takes on the responsibility for the Duchy of Cornwall, which I have undertaken for more than five decades," he began. "Today, I am proud to create him the Prince of Wales, the country whose title I've been so greatly privileged to bear during so much of my life of duty.
"With Catherine beside him, our new Prince and Princess of Wales will, I know, continue to inspire and lead our national conversations, helping to bring the marginal to the centre ground, where vital help can be given."
Amid rumours of a tense relationship, The King send his love to his youngest son Harry and his wife Meghan, who stepped back as senior members of the royal family in 2020 and moved to California.
"I want also to express my love for Harry and Meghan as they continue to build their lives overseas," he said.
During his speech, the monarch shared his "sense of loss beyond measure" and "profound sorrow" over the death of his "beloved" mother and renewed her promise of lifelong service.
After thanking the public for their condolences and support, The King became emotional as he addressed his mother directly.
"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," he stated. "Thank you for your love and devotion to our family and the family of nations you have served so diligently all these years. May flights of angels sing thee to thy rest."
Earlier on Friday, the monarch and his wife, Camilla, Queen Consort, returned to London from Scotland, where The Queen died, and greeted members of the public outside the gates of Buckingham Palace.
Although Charles automatically became King upon the death of his mother, he will be formally proclaimed the monarch at the Accession Council at 10am local time on Saturday at St James's Palace.