In this myth the castle of Vortigen kept falling down. Merlin explained that it was because there were two dragons under the foundations, one red and one white. ( In the picture the two caves beneath the castle where the dragons lived can be seen.)

The implication of this myth is that the strength of the land, (dragon-energy), could only be harnessed by a true ruler and Vortigen was not such a man. The red dragon has also been seen as symbolic of the people of Britain driven out by the white dragon representing the Saxons, who Vortigen had allowed into the country.