Disguises and impersonations appear often in Tristan and Iseult by Rosemary Sutcliff. They add to the story and are important in many of the themes throughout the book.
Tristan has just been wounded, and as a last resort gets in a raft with no steering devices and sets him self to sea. He drifts toward some land, and hears some Irish men speaking, who have been told by the King to kill all men from Cornwall. Tristan has to disguise himself, but since he had little energy to move. Tristan, thinking quick, decides that he will just play his harp, and then the Irish won't suspect him of being from Cornwall. Then the king asks Tristan who he is. Tristan replies that he is Pro of Demester. The king would have killed him anyway, but since Tristan was such a good harper Tristan was spared: "'You shall not die,' said the King, 'for the world would be poorer if your harp were stilled.'"
Tristan has to use disguise to save his life, and is the better off for it. This leads into the love story between Tristan and Iseult.
Tristan is in a ship when he has to use disguise to save his life. King Marc has just found the dark red hair, and has sent Tristan along with some other men off to find the owner of it. The ship is not originally heading for Ireland, but a storm has caught the ship and it is beached on an Irish shore, the very same shore that Tristan drifted onto before. Tristan decides to disguise himself again. People come running from inland and ask Tristan where his ship has come from. Tristan says that he is Tantris and the he and his companions are merchants from Brittany: "'How am I...