King Charles III delivers first address

Britain's King Charles pledged to give lifelong service to the people of the United Kingdom and his other realms in a solemn address to the nation a day after the death of his mother Queen Elizabeth.

"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," the King said.

"And wherever you may live in the United Kingdom, or in the realms and territories across the world, 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."

Offering words of comfort following the death of his mother, the King paid tribute to her "love, affection, guidance, understanding and example".

"Queen Elizabeth was a life well lived; a promise with destiny kept and she is mourned most deeply in her passing. That promise of lifelong service I renew to you all today," he added.

"Throughout her life, Her Majesty The Queen - my beloved mother - was an inspiration and example to me and to all my family, and we owe her the most heartfelt debt any family can owe to their mother."

His Majesty also dedicated part of his address to other senior royals, including his wife and children.

He praised his "darling wife" Camilla, now Queen Consort, and his eldest son and heir William and his daughter-in-law Kate, on whom he bestowed the titles of Prince and Princess of Wales.

"With Catherine (Kate) 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," the King said. 

The new monarch also expressed his love for his younger son Harry and daughter-in-law Meghan, a significant gesture towards a couple whose relationships with the rest of the royal family have been strained.

Charles, who became Prince of Wales in 1958, automatically became king on the death of his mother, Queen Elizabeth, on Thursday.

A memorial service for the Queen was held at St Paul's Cathedral, with 2,000 members of the public joining politicians including the prime minister.