I’m not sure how King Arthur ended up there, but there are at least a couple of stories that suggest there are tunnels under Richmond, hiding a secret army.
Once upon a time, in the town of Richmond, lived a man called Potter Thompson. Generally a cherry soul, and well-liked by most people, but his wife was not ‘most people’. She rarely had a good word to say to him, scolding him whatever he did, or didn’t, do.
One evening, after a long and tiring day making pots, his wife was in a particularly bad mood. Potter was in no mood to spend any time in his own house, but instead wandered off down to the river, even considering throwing himself into the waters below the castle.
As he walked along the bank of the river, he spotted an opening in the cliffs that somehow he had never seen before, and, his wife forgotten, climbed into it. He went slowly and cautiously down the passage revealed, with the darkness slowly swallowing him, until a faint glow appeared ahead.
Turning a corner, this faint light revealed itself as a vast lamp, hung in the centre of a huge chamber. Immediately below the lamp was a stone table, with a great sword within its scabbard and a richly decorated horn.
Coming up to the table, he spotted statues lining the far side of the chamber. They looked like mighty stone warriors, lying on the floor in a row, with one wearing a simple crown of gold. Increasingly nervous now, Potter Thompson walked closer to them and realised they were not made of stone, but were sleeping men, breathing heavily and more slowly than normal men normally do.
Nervously he returned to the table, his hands attracted remorselessly towards the sword and horn. He put the horn around his neck and picked up the sword. As he started to draw the sword from its scabbard, the knights stirred slightly in their magical sleep. He lifted the horn to his lips, and again they stirred before he could blow.
This so terrified him, that he dropped them straight back onto the stone table and turned to run from the secret chamber. Immediately a strong wind rushed through, as though speeding him on his way, and an unearthly cry sounded around him:
‘ If thou hadst either drawn
The sword or sound that horn,
Thou hadst been the luckiest man
That ever was born.’
Thus the King Arthur and his nights were allowed to fall back into their long sleep, and the day when they would rise again and come to England’s aid was delayed. Perhaps one day soon a bolder man shall find again the gloomy vault, and draw the sword and sound the horn, still laid up, and awaiting, beneath Richmond’s historic keep.