Catherine, Princess of Wales dropped out of a planned engagement at Royal Ascot at short notice on Wednesday.
Kate, 43, had been expected to join her husband Prince William as well as King Charles and Queen Camilla in the traditional carriage procession at the racecourse.
She is understood to be disappointed at missing the event in Berkshire, just outside of London, but is working to find the right balance as she returns to public duties after her cancer treatment.
The royal has been making a phased return to official duties since she announced in September that she had completed her chemotherapy. In January, she revealed her “relief to now be in remission,” adding that she remained focused on her recovery.
Kate has undertaken a number of engagements in recent weeks including attending two major events in the royal calendar, the Trooping the Colour parade in London and the Order of the Garter service in Windsor.
This is a developing story and will be updated.