While Queen Elizabeth and Prince Philip first crossed paths as children in 1934, the official start of their romance began in 1939. That year, the two met again while Elizabeth’s family was visiting the Royal Naval College, the institution where Philip was a cadet in training. After corresponding for a number of years, Philip officially asked Elizabeth’s father, King George, for the then-princess’s hand in marriage. The couple subsequently announced their engagement on July 9, 1947. However, in the book, Elizabeth and Philip, Tessa Dunlop, a British historian, wrote that Philip’s mother, Princess Alice, witnessed a “rapid transformation in her son” after the duo disclosed their plans to wed, according to the Daily Mail.

Prior to their engagement, Dunlop wrote that Philip reportedly maintained a high level of excitement and eagerness for the future. However, in the moments after the couple shared their news, it became clear that he had assumed his role as a member-to-be of the British royal family. “Overnight her son made the transition and it was with a note of satisfaction that Alice wrote to her brother Dickie [Lord Mountbatten] in India: ‘It amused me very much to be waiting with the rest of the family, for Philip to come down grandly with Bertie, Elizabeth and Lillibet,'” Dunlop wrote.

Philip proposed to Elizabeth with a three-carat diamond surrounded by 10 smaller diamonds. The piece even featured a connection to Alice’s own wedding day, as the stones were sourced from a tiara that she had worn as a bride.

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Yet, even though his mother witnessed this transition in a matter of days, in actuality, such a switch was likely months in the making. While the duo formally announced their engagement in July 1947, they had already agreed on their plans to wed a year prior—in 1946. Even though King George reportedly approved of Philip, he was concerned that the duo’s romance would be short-lived. As a result, he asked the couple to wait until the then-princess’s 21st birthday before announcing their intentions to the public.

There was no doubt that the couple was eager to wed after disclosing their engagement. They tied the knot a little over four months after the announcement—on November 20, 1947—at Westminster Abbey. The occasion was the first major event for the royal family following the end of World War II. Not wanting the celebration to feel too opulent or pompous, the king insisted that the couple host a smaller affair, inviting just 150 guests to the ceremony and subsequent luncheon at Buckingham Palace.