Before Star Wars: The Last Jedi was released, it was rumored that Princes William and Harry had visited the set and would have cameos in the movie as Stormtroopers. We later learned that, unfortunately, their cameos had been cut from the movie.
The reason? Their height.
A source close to the production recently revealed the specifics of why the cameo appearnces were cut: "Stormtroopers have to be exactly 5ft 11in. At the time we shot it I think the feeling was that the scene would make the final movie. The scene just didn't work for the final cut so it was left out."
The scene that was cut featured the Princes, along with actor Tom Hardy and singer Gary Barlow, playing Stormtroopers who were escorting the characters Finn, Rose, and DJ into an elevator. John Boyega (Finn), Hardy, and Barlow are all 5ft 9in, while Prince William is 6ft. 3in, and Prince Harry is 6ft. 1in. With Boyega's character Finn having been a Stormtrooper in the previous movie, and Hardy and Barlow's heights matching his, it made the Princes appear much taller than the average Stormtrooper and caused them to stand out in the scene.
We may still get to see the Princes in action in the deleted scenes included on the Star Wars: The Last Jedi Blu-ray release, as we've been promised between 20 and 30 minutes of bonus material.