I heard this story when I was a lad from my father and grandfather; no mention of it was ever made in school.
The geezer in the muddy boots is Dr. Orville Ward Owen a medical doctor from Detroit, the date is May 1911, the place is close to the low tide mark of the River Wye in the shadow of the walls of Chepstow Castle.
What led the man to this place was never explained to me back then, although what he sought was well known to my relatives, and their view was that he was wasting his time and money. He made several visits, one lasting longer than six months. In all twelve or fourteen shafts were driven into the river bottom, some deeper than twenty feet. All he found were some heavy timbers that were the remains of a Roman landing stage, these were not what he was looking for.