It is the hottest day of the year so far in Scotland and crowds escape the melting heat in the dark, hallowed vaults of Rosslyn Chapel. Copies of The Da Vinci Code are clutched in sweaty hands. Tourists take photos "to show the folks back home," while others admire the architecture. Beside the south door of the chapel is a group looking intently at what is described as a Templar gravestone. They are here in search of the grail. The Holy Grail made its first appearance in a 12th century romance by Chretien de Troyes. The story grew legs with Wolfram von Eschenbach's 13th century epic poem Parzival where, for the first time, the Knights Templar entered the frame. "Grail questing" has reached fever pitch since Dan Brown's 2003 best-seller, which culminates in Rosslyn. A weekend workshop at nearby Newbattle Abbey College offers enlightenment to grail aficionados. Their guest speakers number a Knight...