King Charles hailed the work of the Commonwealth in its 75th anniversary year on Monday, although the British monarch was absent from annual celebrations for the organisation he leads as he recuperates from cancer treatment.
The Commonwealth Day events are the most significant annual royal occasion that Charles, 75, has missed since he was forced to postpone public appearances while he undergoes treatment for an unspecified form of cancer.
His wife Queen Camilla instead led senior royals at a service at London's Westminster Abbey, which was to be followed by a reception at the Commonwealth's international headquarters.
Usually a highlight of the royal calendar, Monday's event was also overshadowed by a furore over a picture released on Sunday by Kate, 42, wife of heir to the throne Prince William.
She apologized on Monday for issuing an edited photograph of herself with the couple's three children after several leading news organisations including Reuters withdrew it, saying it did not meet their editorial standards.
Like the king, Kate did not attend the service as she continues her recovery from abdominal surgery, attending a private appointment in London instead.
Despite his absence, Charles did appear via a pre-recorded video message to pay tribute to the work of the Commonwealth, a voluntary club of 56 nations which evolved out of the British empire and was set up in its current form in 1949.
"As I have said before, the Commonwealth is like the wiring of a house, and its people, our energy and our ideas are the current that runs through those wires," Charles said in his message.
For most of its existence, the Commonwealth, one of the world's biggest international organisations covering 2.5 billion people, was led by Charles' late mother Queen Elizabeth who was instrumental in its creation and regarded it as one of her proudest achievements.
"Having recently celebrated my own 75th birthday, it warms my heart to reflect on the way the Commonwealth has been a constant throughout my own life – a precious source of strength, inspiration, and pride," Charles said in his message.
"In recent weeks, I have been most deeply touched by your wonderfully kind and thoughtful good wishes for my health and, in return, can only continue to serve you, to the best of my ability, throughout the Commonwealth."