The Abbey of San Galgano in Tuscany

A mysterious "sword in the stone" said to have been thrust into a rock near Siena by a medieval knight proves that the legend of King Arthur, Excalibur and the Holy Grail originated in Tuscany, not Cornwall or Brittany, an Italian scholar claims.

The sword, of which only the hilt and an inch or two of blade is visible, is preserved at the Gothic abbey of San Galgano at Montesiepi, about 19 miles (30 km) southwest of Siena. The Cistercian abbey, now ruined, was built to honor St Galgano, a 12th-century Tuscan nobleman named Galgano Guidotti who renounced a life of "arrogance, lust and violence" to become a hermit after seeing a vision of the Archangel Michael.

To symbolize his rejection of war, he supposedly plunged his sword into the rock, which miraculously "parted like butter", leaving only the hilt exposed to form the shape of the Cross.

It has been assumed that the Tuscan "sword in the stone" is a fake, made to echo the Celtic legend of King Arthur as told by Geoffrey of Monmouth and Chretien de Troyes and by Thomas Malory in his celebrated 15th- century Le Morte Darthur.

But a study by the medieval historian Mario Moiraghi suggests that the story of St Galgano and his sword was the origin of the myth of King Arthur and the Knights of the Round Table, embellished by medieval troubadours as it spread from Tuscany.