Shortly after the flag began to fly, certain members of the royal family quickly left the special seats from which they’d been watching the pageant and disappeared, another sure sign that the Queen was planning to appear.

Why? The members in question were the future kings and their families. Prince Charles and his wife Camilla, Duchess of Cornwall. Prince William, Duke of Cambridge, his wife Catherine, Duchess of Cambridge, and their children Prince George, Princess Charlotte, and Prince Louis. (Charles, William, and George are the future kings, in case you were wondering.)

And sure enough, in a few minutes, they appeared with the Queen on the balcony of Buckingham Palace.

Source: https://www.buzzfeed.com/ellievhall/queen-elizabeth-jubilee-surprise-appearance