The sword was until recently thought to be fake [photo: Enigma Galgano]

In The Enigma of San Galgano, Mario Moiraghi cites scientific tests which date a sword embedded in a rock in an abbey in Tuscany to the year 1180, decades before the first literary reference to the sword.

He adds that an inquiry which led to the canonisation of Saint Galgano, the knight believed to have put the sword in the stone, contains a series of facts identical to the legend of Sir Percival, the finder of the Holy Grail.

In a previous book, Mr Moiraghi suggested that other elements of Arthur's legend originated in Persia.

Details such as the presence in the legend of ostriches, lions and mongeese - which never inhabited that part of Europe - suggest that it originated in tales of chivalry brought from the east by merchants, he says.

Hermit

The sword of St Galgano is preserved at a Gothic abbey of the same name at Montesiepi, near the city of Siena.

King Arthur's legend may not be wholly from Celtic lands

Only the hilt and a few centimetres of the sword's blade protrude from the rock.

Galgano was said to be a violent and lustful knight who became a hermit after seeing a vision of Jesus, Mary and the Apostles.

According to legend, he miraculously plunged the sword into the rock after being invited to renounce all worldly goods.

The sword was for many years considered a recent fake, but metal dating research at Pavia university two years ago established its authenticity.

Holy Grail

In the Arthurian legend, the future king pulls the sword from the stone to herald his accession to the throne.

Most elements of the legend have generally been thought to be Celtic in origin - from Wales, Cornwall or the French region of Brittany.

However, hard evidence of Arthur's existence as a historical figure in these regions is thin.

Mr Moiraghi says Galgano's life inspired two poetic versions of the Holy Grail story written shortly afterwards.

Chretien de Troyes' Perceval (1190) and Wolfram von Eschenbach's Parzival (c. 1220) both tell of a knight who overcomes all obstacles to reach his ideal.