Roman de Brut (c. 1155) was based on the Historia Regum Britanniae of Geoffrey of Monmouth. Its popularity is explained by the new accessibility to a wider public of the Arthur legend in a vernacular language. Wace was the first to mention the legend of King Arthur's Round Table and ascribe the name Excalibur to Arthur's sword, although he on the whole adds only minor details to Geoffrey's text. The Roman de Brut became the basis, in turn, for Layamon's Brut, an alliterative Middle English poem, and Piers Langtoft's Chronicle.