This is not a historical drama, nor a biopic. It is an allegory which mixes and unsolved murders from the 1480s with costumes and customs from the 1930s, to make an artistic statement about the similarities between these two eras. While the movie portrays several historical figures, they are not intended to perfectly resemble their real-life counterparts, and their words and actions are never claimed to be what the real people said and did.
As Edward finishes his dance with Queen Elizabeth (at the beginning) and they walk off the dance floor, the young prince slips and falls.