Who is Duke of Tintagil?

The Duke of Tintagil is a fictional character from the 1965 children's book "The Adventures of Tintin: The Seven Crystal Balls" by Hergé, where Tintin encounters a variety of characters during his adventures. However, there is no widely recognized Duke of Tintagil in historical or contemporary contexts outside of this reference. The title may also be used in various fictional works or adaptations. If you are looking for a specific interpretation or context, please provide more details!