The castle at Eilean Donan was featured but it was a pile of rubble in 1745/46, having been bombarded by ships of the Royal Navy on 10 May 1719.
After the death of his first wife Primmie in an accidental fall, David Niven was desperate to quit Hollywood and return to his native England. He recorded an audition in full costume as a way of persuading Samuel Goldwyn to let him out of his contract and loan him to Alexander Korda. In later years, Niven said that Goldwyn had actually pressured him to make the film.
The real Prince Charles Edward Stuart was only 24-25 at the time of the Jacobite Uprising.
Soldiers from the British army were drafted in as extras. They were not paid for this work.