High Quality Content by WIKIPEDIA articles! Sir Launfal is a 1045-line Middle English romance or Breton lay written by Thomas Chestre dating from the late-14th century. It is based primarily on the 538-line Middle English poem Sir Landevale, which in turn was based on Marie de France`s lai Lanval, written in a form of French understood in the courts of both England and France in the 12th century. Sir Launfal retains the basic story told by Marie de France and retold in Sir Landevale, augmented with material from an Old French lai Graelent and a lost romance that possibly featured a giant named Sir Valentyne. This is in line with Thomas Chestre`s eclectic way of creating his poetry.