The 86-year-old monarch was filmed leaving Buckingham Palace in a helicopter with current James Bond portrayer Daniel Craig, then appeared to parachute into the opening ceremony of the Summer Olympics -- actually a stunt double.
The Daily Telegraph quoted Angela Kelly -- personal assistant, adviser and curator to the queen for nearly 20 years -- as saying the stunt was kept top-secret and even the monarch's other dressmakers didn't know why two of the same peach cocktail frocks were being made.
Kelly said she worked closely with director Danny Boyle's team to ensure the dresses worn by the queen and her stunt double were exactly the same.
"The Buckingham Palace dressmakers worked quietly for months, never having both dresses out of storage at the same time," Kelly wrote in her new book, "Dressing the Queen: The Jubilee Wardrobe." "Even they did not know why two dresses were required for the same event."
Kelly said the color of the dress was chosen because it was bright enough to be seen as "the queen" descended into the stadium and was not associated with any of the participating Olympic nations, the Telegraph reported.