With thousands of mourners in London to pay their respects to the late monarch, the King followed his mother's coffin in a sombre walk towards Westminster Abbey.
Dignitaries from around the world have descended on the more than 1,000-year-old abbey to say goodbye to Queen Elizabeth II after her remarkable 70-year reign.
And the King, flanked by his family, was visibly moved by the outpouring of love and emotion on display.
His siblings Princess Anne, Prince Andrew and Prince Edward also followed – while Prince William and Prince Harry put aside any personal differences to respect their beloved grandmother.
The Duke of York and the Duke of Sussex, who are no longer working royals, wore suits as they marched behind the carriage.
King Charles III leading members of the Royal Family JOHN SIBLEY
The King looked visibly moved Hannah McKay
All looked sombre as they followed the carriage.
There was complete silence from the crowd close to Parliament Square, as the State Gun Carriage carrying Queen Elizabeth II’s coffin slowly moved past.
The crowd, momentarily still and with phones held aloft to capture the moment, was around 10-people thick in places, as tens of thousands thronged the streets to say goodbye to the monarch.
The short procession from Westminster Hall, to the sound of bagpipes and with Big Ben tolling, took around eight minutes.
During the service, the Archbishop of Canterbury hailed the Queen’s “abundant life and loving service” as he delivered the sermon at her state funeral, adding: “She was joyful, present to so many, touching a multitude of lives.”
After proceedings concluded in the historic abbey, the procession set off for Wellington Arch at Hyde Park Corner.
The state hearse will later depart on its journey to Windsor as the parade gives a royal salute and the National Anthem is played.
The King, joined by Queen Consort Camilla and other members of the Royal Family, will then depart for Windsor by car.
King Charles III in his state car on Monday PETER CZIBORRA
A committal service will take place in Windsor Castle's historic St George's Chapel this afternoon, after which members of the Royal Family will depart the Galilee Porch and bring a close to the public ceremonial arrangements.
A private burial service will be conducted by the Dean of Windsor at 7.30pm, attended by the King and members of the Royal Family.
Queen Elizabeth II will then be buried together with her beloved Prince Philip, Duke of Edinburgh, at the King George VI Memorial Chapel.