Estoire del saint Graal
The Estoire del San Graal was a literary work from the 13th century. It is the story of Joseph of Arimathea brining the Grail to Britain.In this story, the Grail is the vessel ('escuele', a bowl) used by Christ at the Last Supper, which Joseph of Arimathea takes from the Upper Room and uses to collect Christ's blood at the Entombment. 

Thereafter follow many adventures and wanderings, in which Joseph and his son Josephé, who becomes the first Christian bishop, achieve many conversions, notably that of King Evalach who takes the baptismal name of Mordrain.  With his brother-in-law Nascien (known as Seraphe until his conversion), Mordrain undergoes many trials in battle, at sea, and on islands, encountering enchanted boats manned in turn by Christ and the devil.

The Estoire branch of the Lancelot-Grail romance is based on a verse text composed c. 1200 by an author who names himself Robert de Boron.  Only one copy of Robert's verse version survives