As documented in Oscar-winning film The King's Speech, the Queen Mother was King George VI's rock, and fiercely protective of her husband.
But there was a time she wasn't sure if she wanted to marry him at all.
Private letters written by a young Elizabeth Bowes Lyon, revealed in a new book approved by the Queen to mark her Diamond Jubilee, show her reluctance.
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After a three-year courtship, the future Queen Elizabeth wrote to one of her closest friends in January 1923, saying she felt "terrified" at the prospect of marrying into the royal family.
This was after she finally accepted his proposal, having turned him down in the past.
In another letter dated February 28, 1921, Elizabeth apologises to the Duke after knocking him back.
"Dear prince Bertie," she writes, using the name she affectionately called him, "I must write one line to say how dreadfully sorry I am about yesterday. It makes me miserable to think of it."
Elizabeth goes on to ask: "Anyway, we can be good friends can’t we?
The pair did wed, in 1923, and went on to have two daughters, Elizabeth and Margaret Rose.
Of course at the time, the couple did not know Bertie would be forced to take the throne after his brother Edward VIII abdicated in order to marry American divorcée Wallis Simpson in 1936.
On October 28, 1926, Elizabeth wrote to her mother, Lady Strathmore, with news of the six-month-old Princess Elizabeth, who unknown to them both would be the future Queen.
"She is going to be very wicked, and she is very quick, I think," she wrote.
Letters written by the Queen Mother, from her childhood till her death in 2002 – when she was 101, can be read in William Shawcross' new book Counting One's Blessing: The Selected Letters of Queen Elizabeth the Queen Mother.