King Charles III spoke about his responsibility to the Church of England and his own personal faith in a moving first address to the nation as sovereign following the death of his mother, Queen Elizabeth II, on Thursday.
The address was broadcast live nationwide and on large screens erected in St Paul's Cathedral for a service of prayer and reflection that was attended by 2,000 people, including Prime Minister Liz Truss.
As Britain's new monarch, King Charles inherits the titles of Supreme Governor of the Church of England and Defender of the Faith.
King Charles said that his faith was "deeply rooted" in the Church of England and that it had taught him to "cherish a sense of duty to others".
"The role and the duties of Monarchy also remain, as does the Sovereign's particular relationship and responsibility towards the Church of England - the Church in which my own faith is so deeply rooted," the King said.
"In that faith, and the values it inspires, I have been brought up to cherish a sense of duty to others, and to hold in the greatest respect the precious traditions, freedoms and responsibilities of our unique history and our system of parliamentary government.
"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."
Earlier in his address, the King thanked his "darling mama" for her 70 years of service to the UK and Commonwealth.
"In her life of service we saw that abiding love of tradition, together with that fearless embrace of progress, which make us great as nations. The affection, admiration and respect she inspired became the hallmark of her reign," he said.
"And, as every member of my family can testify, she combined these qualities with warmth, humour and an unerring ability always to see the best in people.
"I pay tribute to my Mother's memory and I honour her life of service. I know that her death brings great sadness to so many of you and I share that sense of loss, beyond measure, with you all."
He said he would endeavour to serve the people of the UK, the Realms and Commonwealth "with loyalty, respect and love", before ending with a nod to his late father, Prince Philip, and a quote from Shakespeare's Hamlet.
"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," he said.
"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 thy rest'."