Princess Alexandra made a rare public appearance as she joined the King at a special church service in London on Wednesday evening.
The late Queen Elizabeth II's cousin, 88, was pictured seated next to Charles, 76, in the Queen's Chapel as the royals marked its 400th anniversary.
Alexandra, who is known as the Honourable Lady of Ogilvy, was last seen publicly as she attended the King's Christmas lunch for extended family at Buckingham Palace last December.
She is still listed as a working member of the royal family but has taken a step back from full-time public duties in recent years.
According to the Court Circular, some of Alexandra's last major engagements were attending the King's coronation, presenting medals to members of The Royal Lancers (Queen Elizabeth's Own) in her role as Deputy Colonel-in-Chief, and visiting the Chelsea Flower Show – all in 2023.
She was also among the royals at a thanksgiving service in Windsor for the late King Constantine of Greece in February 2024, accompanied by her daughter, Marina Ogilvy
The service at the Queen's Chapel featured music by the Gentlemen and Children of His Majesty’s Chapel Royal Choir, accompanied by the Duchess of Edinburgh's String Orchestra and the State Trumpeters of the Household Cavalry Band.
It reflected the chapel's early role as a place of worship for European courtiers.
After the celebration, the King viewed a newly commissioned piece of altar plate – the His Majesty King Charles III Ciboria – the first addition to the chapel's silverware since 1688.
All about Alexandra
Born on 25 December 1936, Alexandra is the only daughter of the late Prince George, Duke of Kent and Princess Marina of Greece and Denmark. She has two brothers - Prince Edward, Duke of Kent, 89, and Prince Michael of Kent, 82.
On 24 April 1963, she married The Hon. Angus James Ogilvy at Westminster Abbey and the couple went on to have two children – James and Marina Ogilvy.
Alexandra has four grandchildren – James's children, Flora Vesterberg and Alexander Ogilvy, while Marina is mother to Zenouska and Christian Mowatt.
She still lives at Thatched House Lodge in Richmond, London – the home she shared with her husband, who died in 2004.
Princess Alexandra, who was very close to her cousin, the late Queen, spent much of her working life carrying out engagements in relation to her partonages and charities – from the arts to medical care.