The oldest member of the British royal family, Katharine, Duchess of Kent, died on Thursday aged 92, Buckingham Palace has announced.
The duchess was married to Prince Edward, 89, the Duke of Kent, who is a first cousin to the late Queen Elizabeth II.
Katharine had not been a working royal since 2002 and, in some ways, she broke the strict mould of a family that has become known as the Firm.
Public appearances have been rare in recent years. For instance, she did not attend the funeral of Queen Elizabeth II or the coronation of King Charles III.
The duchess was in 1995 the first British royal to convert publicly to Catholicism despite centuries-old laws which stipulated only Protestants, and people married to Protestants, could succeed to the crown.
She also had a secret job as a music teacher at Wansbeck Primary School, in Hull, for a time, after stepping back from official royal duties.
Katharine died "peacefully" at Kensington Palace on Thursday night "surrounded by her family", the official announcement said.
"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 statement from Buckingham Palace read.
King Charles III and Queen Camilla were not at Kensington Palace when she died. The royals are still at Balmoral Castle, in Scotland, where they traditionally spend the British summer.
The king has approved a period of royal mourning until the day of Katherine's funeral, the date of which has not yet been announced.
It means members of the royal family and their staff will wear appropriate clothing for the foreseeable future.
The duchess was synonymous with the Wimbledon tennis championships, where she regularly handed out trophies. She also famously consoled a distraught Jana Novotna after she lost the women's final on centre court in 1993.
While working at Wansbeck Primary School, she enjoyed complete anonymity despite being married to a senior royal.
"I was just known as Mrs Kent," she told The Guardian in 2014.
"Only the head knew who I was. The parents didn't know and the pupils didn't know.
"No-one ever noticed. There was no publicity about it at all. It just seemed to work."
She is survived by her husband and three children, George Windsor, Earl of St Andrews, Lady Helen Taylor, and Lord Nicholas Windsor.
The Prince and Princess of Wales released a statement saying Katharine "worked tirelessly" and would be "much missed", while British Prime Minister Keir Starmer said the late royal "brought compassion, dignity and a human touch to everything she did".
