The stark-white dress had quarter-length sleeves and a dramatic train, and Meghan looked like a member of the royal family thanks to the veil and tiara she wore with the elegant gown.
Meghan changed into a halter-style dress from Stella McCartney for the reception, which was also white.
"The Queen was surprised that Meghan wore pure white on her wedding day," an unnamed source told Nicholl for the book, as her marriage to Harry wasn't her first.
"Perhaps it's a generational thing, but she believes if you've been married before, you wear off-white on your wedding day, which is what the Duchess of Cornwall did," the source went on to tell Nicholl of the Queen's thoughts on wedding fashion.
Indeed, Camilla, the Queen Consort, wore a cream dress and coat from Robinson Valentine to her and King Charles III's civil ceremony in 2005, and she changed into a light-blue dress for the blessing of her and King Charles' marriage.
Nicholl's book also notes that there was tension in the royal family in the weeks leading up to Harry and Meghan's wedding, pointing to the argument between Meghan and Kate Middleton, the Princess of Wales, over Princess Charlotte's flower girl dress.
Lady Elizabeth Anson, the Queen's late cousin, also told Nicholl that Prince Harry "shouted" at the Queen's royal dresser Angela Kelly in the days leading up to his and Meghan's wedding.
"What Meghan wants, Meghan gets," he yelled as Anson told Nicholl, leading the Queen to give him a "stern telling-off."
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