Their engagement became official on 24 February 1981. Diana selected a large engagement ring that consisted of 14 solitaire diamonds surrounding a 12-carat oval blue Ceylon sapphire set in 18-carat white gold, which was similar to her mother's engagement ring. The ring was made by the Crown jewellers Garrard. In 2010, it became the engagement ring of Catherine, Duchess of Cambridge. The Queen Mother gave Diana a sapphire and diamond brooch as an engagement present.  Following the engagement, Diana left her occupation as a kindergarten assistant and lived for a short period at Clarence House, which was the home of the Queen Mother. She then lived at Buckingham Palace until the wedding. Diana was the first Englishwoman in 300 years to become the spouse of an heir apparent, and she was also the first royal bride to have a paying job before her engagement. She made her first public appearance with Prince Charles in a charity ball in March 1981 at Goldsmiths' Hall, where she met the Princess of Monaco.  Twenty-year-old Diana became Princess of Wales when she married the Prince of Wales on 29 July 1981 at St Paul's Cathedral, which offered more seating than Westminster Abbey, a church that was generally used for royal nuptials. The service was widely described as a "fairytale wedding" and was watched by a global television audience of 750 million people while 600,000 spectators lined the streets to catch a glimpse of the couple en route to the ceremony. At the altar, Diana inadvertently reversed the order of Charles's first two names, saying "Philip Charles" Arthur George instead. She did not say that she would "obey" him; that traditional vow was left out at the couple's request, which caused some comment at the time. Diana wore a dress valued at PS9,000 with a 25-foot (7.62-metre) train.  After she became Princess of Wales, Diana automatically acquired rank as the third-highest female in the United Kingdom Order of Precedence (after the Queen and the Queen Mother), and was fifth or sixth in the orders of precedence of her other realms, following the Queen, the relevant viceroy, the Duke of Edinburgh, the Queen Mother, and the Prince of Wales. Within a few years of the wedding, the Queen extended Diana visible tokens of membership in the Royal Family; she lent the Princess the Cambridge Lover's Knot Tiara, and granted her the badge of the Royal Family Order of Queen Elizabeth II.

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The service was widely described as a "fairytale wedding" and was watched by a global television audience of 750 million people