King Mark of Cornwall was said to be the son of King Felix, who died after an Irish raid on his castle at Tintagel. In Arthurian legend Mark is portrayed as violent, treacherous and cowardly. He was said to have ruled Cornwall in the early 6th century. Legend describes him as cousin of King Arthur and uncle of Tristan. Mark sent Tristan to fetch his young bride, Isolde (or Iseult) from Ireland. Tristan and Isolde fell in love with a little help from a magic potion and their story has been told again and again. More modern versions of the legend include some by Thomas Hardy, John Masefield, Sir Arthur Quiller-Couch, John Erskine and John Updike.
There is some evidence for an actual historical figure who ruled Cornwall in the Dark Ages, such as that of the Welsh nobleman, March son of Meirchyawn. In the 9th century “Life of Paul Aurelian”, Cunomorus ruled Cornwall in the early sixth century. Mark has been identified with this king who was believed to have had his seat at Castle Dore, near Fowey. Cunomorus is associated with Tristan on the famous Tristan Stone near Fowey, which commemorates Drustanus, son of Cunomorus.