In reality, Lady Jane and Guilford Dudley barely knew each other and were not together during their imprisonment.
Cary Elwes is related to both Guilford Dudley and Lady Jane Grey (on his father's side). Because Dudley and Grey never had children, Elwes is the direct descendant to Dudley and Grey's siblings: Mary Dudley, Guilford's sister, and Katherine Grey, Jane's sister, who was also the wife of Edward Seymour.
The film portrays Jane as a dark eyed, dark haired girl when in actuality, Lady Jane Grey was very fair with blond hair and light eyes. She was described as very pleasant looking except for her freckles, which were considered unbecoming on a young lady at the time.
Thomas Wyatt was the leader of the rebellion, proclaiming her Queen of England. Her father, Henry, was a part of this rebellion.