Eugenie and Jack, who met in 2010 in the ski resort of Verbier, have chosen to get married in Windsor at St George's chapel just like the Duke and Duchess of Sussex in May.
Cara showed up in a top hat and tails to the wedding at St George's chapel in Windsor, where Meghan and Harry were Wednesday earlier this year.
As with any large-scale royal event (including the wedding of the Duke and Duchess of Cambridge), there has been a petition calling for Eugenie and Jack to pay for their own wedding. Only eight years old at the time, the youngster looked simply adorable in a white bridesmaid dress, and joined the family while waving to well-wishers on the Buckingham Palace balcony.
One noticeable absentee was Camilla, the Duchess of Cornwall, the wife of heir-to-the-throne Prince Charles, as she was carrying out an engagement in Scotland.
Gusty wind required Eugenie to walk carefully up the steps leading to St. George's Chapel as she was escorted by her father, Prince Andrew.
The crowds caught a glimpse of the bride and her wedding dress.
Princess Eugenie, the granddaughter of Queen Elizabeth II, is set to marry tequila company executive James Brooksbank on Friday morning, but the second royal union of the year seems to have less interest than Prince Harry and Meghan Markle's May celebration.
Eugenie and the groom, Jack Brooksbank, will be taking a carriage ride through the streets of Windsor. Her sister, Princess Beatrice, will be maid of honour.
About 1,200 members of the public have been given balloted invites to the castle's Lower Ward, as have charity representatives, children from Eugenie's old schools, and royal household staff.
The group says Eugenie does not carry out royal duties and that weddings are personal, private occasions, not affairs of state.
But Princess Eugenie hinted that she would be wearing a "British-based designer" in a recent British Vogue interview.
The queen will then host a reception for the couple and their guests at the castle.
The presence of so many royals - and a number of celebrity guests - has prompted extra security measures to be put in place.