Matthew Roydon was a real person associated with Christopher Marlowe and Henry Percy, among others. He was noted by contemporaries as a leading poet of London literary society at the time, though very few of his works survive in print and nothing can be confirmed of his life apart from that.
The hand embroidered redwork coif worn by Susanna Loftus is personally owned by a member of the cast (as a item of re-enactment costume), and was a late addition to the costuming as "happy find" when first shown on set.
Henry Percy, 9th Earl of Northumberland, was nicknamed "The Wizard Earl" for his interest in science and alchemy and his large library.
William Cecil, 1st Baron Burghley, was the chief advisor for Elizabeth I through most of her reign (and manager of her house before her reign). He was staunchly Protestant and known for his persecution of Catholics in the British Isles and his support of foreign Protestants in their fights against the Catholics of their own countries.
William Pole was a historian and antiquary of the County of Devon and Member of Parliament.