Malory briefly mentions a Sir Marrok at the healing of Sir Urry, who was betrayed by his wife and spent seven years as a werewolf." This line seems to refer to the a tale similar to the lai "Bisclavret" by Marie de France, whose hero was cursed to assume the form of a wolf for three days each month -- and worse, if he could not find his clothes at the end of the three days, then he had to remain in wolf form indefinitely.
   Marrok may be the same character as in the oldest Irish Arthurian romance which has a 'werewolf' as leading character: Eachtra an Mhadra Mhaoil. The edition and translation by Macalister was published in 1907 in the Early Irish Texts Society series no. X. It was reprinted a few years ago with a new introduction by J.F. Nagy.