King Mark was the son of King Felix of Cornwall. His father died after a raid on his castle at Tintagel by the King of Ireland and Mark inherited the throne. Thereafter, the relationship with between the two kingdoms remained shaky, with Ireland demanding tribute for Cornwall’s protection. Mark is portrayed throughout Arthurian literature as a violent, treacherous, cowardly and underhand villain. He is supposed to have murdered his own brother in order to take the throne. Poor Prince Bouduin was stabbed through the heart after gaining the love of his people for repelling a Saxon invasion.

The son of Mark’s sister, Isabelle, was Sir Tristram, heir to the Kingdom of Lyonesse. Mark took the young man into his household and, impressed by his prowess of arms, made him his steward. Tristram became a local hero when he defended the kingdom against the Irish champion, Sir Morhaut, who had been demanding tribute on behalf of King Anguish. Shortly afterwards, however, Mark fell out with Tristram over his affair with the wife of Sir Segwarides. The King was so infatuated with the lady himself, that he tried to have Tristram murdered. The young prince never found out the extent of the animosity though and when his mistress went back to her husband, the Cornishmen were soon reconciled. With the Irish in retreat, King Mark entered into a peace treaty with them, to be sealed by his marriage to Princess Isolde. Tristram was sent to escort her to Cornwall, but the two mistakenly drank a love potion intended for the bridal couple. Despite Mark and Isolde’s marriage, Tristram became the new Queen’s lover. They bent over backwards to keep their affair a secret, making great use of Tristram natural talent for disguise. Mark , of course, found out however and a bitter feud with his nephew ensued. Sir Tristram fled his uncle’s sphere of influence with his lover a number of times - notably hiding out for months with Sir Lancelot - but Mark always managed to retrieve his wife, and Tristram was eventually forced to leave for Brittany.

To outwit his nephew, King Mark entered into a number of wicked plans. He begged Tristram’s help against Cornwall’s enemies in order to get him killed or, at least, sent overseas; and even forged letters from the Pope to persuade him to go off on Crusade. Mark killed many of his own knights and also those of King Arthur’s Court, often while in a great rage. At one time he invaded Arthur’s own kingdom, but was beaten back by the Knights of the Round Table.

There are various versions of King Mark’s death, but he is generally thought to have been killed by the revenge-seeking Sir Bellangre le Beuse, a grandson of Mark’s murdered brother.