The Welsh Red Dragon

While at Sygun Copper Mine, I heard about the legend of the Welsh Red Dragon.  The legend goes in King Arthur's time, the King wanted to build  a fort on this hillside by Sygun mountain.  But the walls fell down.  He sent for the wizard.  Who had the earth extracted from the hill, where they found a pool.  When the water was drained they found two sleeping dragons :- a red one and a white one.  The two dragons fought.  And the red dragon drove the white dragon away.  The wizard saying that this prophecised  the celts driving the saxons out of Wales.  According to the legend, this is why there is a red dragon on the  Welsh flag.