The Queen shared a close bond with Princess Margaret from childhood, and no doubt her younger sister was in her thoughts on Wednesday, which marked the 20th anniversary of Princess Margaret's death.
Princess Margaret passed away on 9 February 2002, aged 71, and the monarch shared a heartbreaking statement at the time of the announcement.
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Buckingham Palace said at the time: "The Queen, with great sadness, has asked for the following announcement to be made immediately.
"Her beloved sister, Princess Margaret, died peacefully in her sleep this morning at 6.30am, in The King Edward VII Hospital. Her children, Lord Linley and Lady Sarah Chatto, were at her side.
"Princess Margaret suffered a further stroke yesterday afternoon. She developed cardiac problems during the night and was taken from Kensington Palace to The King Edward VII Hospital at 2.30am. Lord Linley and Lady Sarah were with her, and The Queen was kept fully informed throughout the night.
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Margaret and Elizabeth pictured in 1946
"Queen Elizabeth The Queen Mother and other members of the Royal Family are being informed."
The Prince of Wales also paid tribute to his "darling aunt" in a moving TV interview the day after the announcement, saying at the time: "This is a terribly sad day for all my family, but particularly of course for the Queen, my mama, and my grandmother, the Queen Mother, and also for Princess Margaret's children, David and Sarah, and also my aunt's wonderful friends who, like all of us, miss her deeply."
Princess Margaret, the Queen Mother and the Queen in 2000
Margaret's passing came just three days after the 50th anniversary of her father King George VI's death. A private funeral service was held at St George's Chapel at Windsor Castle for family and friends on 15 February 2002, with a state memorial service taking place at Westminster Abbey in April 2002.
Just seven weeks after the death of her younger sister, the Queen suffered further heartache when the Queen Mother passed away on 30 March 2002, aged 101.
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