https://tinyurl.com/ykbcxrwx "This is the first work of any length in the English language on St. Galgano, an Italian knight who gave up his comfortable life to become a hermit. One particular incident from his life is already known to English speaking audiences, though through entirely other means, namely, the medieval stories of King Arthur. It may come as a surprise that there was a real sword in the stone, which may still be seen in Galgano, Italy. The sword in the stone, though a significant miracle in St. Galgano's life, is but a divine confirmation of his calling to penance, prayer and sacrifice for souls, whereas in Arthurian legend it is centered around the establishment of an earthly kingdom. This introduction into the Arthurian legend is late, around the 14th century, and most certainly has its origin in the story of St. Galgano.
