The Holy Grail: imagination and belief by Richard Barber

That obscure object of chivalric desire

"Whom does the Grail serve?" The haunting riddle was never fully explained by Chrétien de Troyes, who first wrote The Story of the Grail. The tale has inspired eight centuries of high endeavours and, more recently, a host of irreverent usages.

Chrétien lived in northern France at the end of the 12th century. He wrote when the sagas of the Norsemen, the legends of the Celts, the courtly romances of the French and the thuggish war chronicles of the English all mingled in a melting pot of marvels. His stories were colourful and characterful, and hugely popular.

Most famous was his unfinished Roman du Parsifal. Parsifal's encounter with the Fisher King, the blood-tipped lance and the brilliant bejewelled "grail" is one of the most mysterious scenes in literature. Because Parsifal fails to ask what is going on, the Fisher King will not be cured and his lands will be laid waste by enemies.

After five godless years, he meets a hermit who hints at a parable: the grail contains the "host", the body of Christ. The hermit delivers the quadruple whammy that Parsifal's mother died of grief after he left her to become a knight; she was the sister of both the hermit and the mysterious man in the chamber who was served by the Grail - the father of the Fisher King.

Because Chrétien never told us more about Parsifal's career, it could only be guessed at by his "continuers". One introduced Joseph of Arimathea, a Roman soldier given the cup used at the Last Supper, who used it to catch the blood that dripped from Christ's side during the crucifixion. Other continuers explained that the cup was called the "grail" because it delighted [agreer, to delight] those who drank from it. Joseph brought it to England, landing at Glastonbury (then an island).

Soon Gawain, Lancelot and Galahad were added to those who pursued the Grail. Sir Thomas Malory placed the quest for it deep into the political world of King Arthur; a reflection of his own involvement in the troubled politics of the 15th century. But he also preserved its intensely holy character as a symbol of the Eucharist; influenced, Richard Barber surmises, by the Holy Blood of Hailes Abbey and the Coventry mystery plays.

Over the centuries, the surmises have become wilder and wilder. The Grail has been posted back into the Celtic twilight and made the loving cup of secret orders. Tennyson and Wagner wove masterpieces around it. It was owned by the Cathar heretics and contains the DNA of Merovingian kings; it is in Valencia Cathedral, Genoa and Rosslyn Chapel near Edinburgh.

Richard Barber has a masterly grasp of these varied sources, and a gift for lively summary. Monty Python came close to making the Grail an object of ridicule. Barber's book, which restores all its original gravitas and wonder, gives it an exciting new lease of life.