Curious facts about the Knights Templar and the Grail quest:
The Templars were started by Hugh de Payens, cousin of St. Bernard of Clairvaux, who founded the Cistercian Order of monks. The Cistercians would go on to write not only the Lancelot-Grail Cycle, aka the Vulgate Cycle, but also the White Book of Rhydderch in Wales, whose romance Peredur is another version of the Grail romance. Another member of the original knights was Fulk V, grandfather of Henry II of England, husband of Eleanor of Aquitaine. Fulk V was also the last King of Jerusalem.
Henry's cousin Philip of Alsace is the man who supplied Chretien de Troyes with the material for Perceval, the story of the Holy Grail. More interesting, it was the Council of Troyes in 1128 or so that really established the order. A connection? When at least three of the early grail texts name the Templars as guardians of the grail...
Finally, the Knights also help build Oxford, and were there at the same time Geoffrey of Monmouth was busy writing his History of the Kings of Britain, the first major Arthurian work in Latin (excluding Welsh sources--their impact is still being debated).