The Duchess of Kent has died at the age of 92, Buckingham Palace has said.
Katharine - who became the oldest living member of the Royal Family when Queen Elizabeth II died in 2022 - was known for consoling Wimbledon finalists, notably a tearful Jana Novotna in 1993.
A skilled pianist, organist and singer, she dropped her HRH style, preferring to be known as Mrs Kent, and retreated from royal life to spend 13 years teaching music at a primary school in Hull.
The palace said in a statement on Friday: "It is with deep sorrow that Buckingham Palace announces the death of Her Royal Highness The Duchess of Kent.
"Her Royal Highness passed away peacefully last night at Kensington Palace, surrounded by her family.
"The King and Queen and all Members of The Royal Family join The Duke of Kent, his children and grandchildren in mourning their loss and remembering fondly The Duchess's life-long devotion to all the organisations with which she was associated, her passion for music and her empathy for young people."
The Union Flag at Buckingham Palace was lowered to half-mast as a mark of respect shortly after the duchess's death was announced. A formal framed announcement is displayed on the palace railings.
An online condolence book will be available in the coming days and funeral details will be announced in due course.
Katharine married Prince Edward, the Duke of Kent - who is the cousin of the late Queen Elizabeth II - in a grand ceremony at York Minster in 1961.
The couple have three surviving children, George, Earl of St Andrews, Lady Helen Windsor, and Lord Nicholas Windsor.
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The duchess suffered heartbreak when she was forced to have a termination after catching German measles while pregnant in 1975. Two years later, she endured the devastation of giving birth to a stillborn son, Patrick.
She led a separate life from the Duke of Kent for many years but the couple did not divorce - and were said to be closer than ever after Edward suffered a stroke in 2013, which prompted his wife to move back into their Kensington Palace home.
Katharine's famous Wimbledon moments
Her appearances at Wimbledon, where she presented the winners' trophies, became a familiar feature of the summer sporting calendar.
In 1993, she put royal formalities and protocol aside to hug tearful runner-up Jana Novotna after she lost the ladies' singles final to Steffi Graff.
Her relationship with Wimbledon authorities later soured, when she was refused permission to take the young son of murdered headmaster Philip Lawrence into the royal box at the tournament.
(c) Sky News 2025: Katharine, Duchess of Kent, dies aged 92