During the fifth century, the Celtic King Vortigern was being hard pressed by the invading Anglo Saxons, and so decided to build a stronghold in Snowdonia. He chose to build the fort on a domed shaped hill near the settlement of Beddgelert, and set his royal stone masons to work. The stone masons started building quickly and with good heart, but when came the next sunrise they discovered that all their building materials had mysteriously vanished.

The same thing occured on the following morning, and yet again the morning after that; on each occasion the materials had simply vanished overnight. Angry and frustrated with the lack of progress, Vortigern consulted his magicians and sorcerors. They told the King that he would only be successful in building the fort if he sprinkled the foundations with the blood of a boy born without a father.

One such "Wonderchild" - born of a human mother and an Otherworld father - was a boy known as Myrddin, who lived close by. He was duly brought before Vortigern, and made ready for the sacrifice.

However, Myrddin was, in fact, Merlin the magician who possessed a great many magical powers and had the gift of vision. He told the king that the foundations of his fort were being undermined by a subterranean lake, in which two dragons lay in slumber.

Vortigen's own magicians advised him to ignore the boy's words and carry out the sacrifice as planned. But Vortigern was uncertain. He eventually decided to heed to boy, and had his labourers dig deep beneath the foundations.

Just as Myrddin had said, beneath the foundations of the fort was a large underground lake. Orders were given for it to be drained, and two sleeping dragons were discovered - one white and one red.

The dragons awoke and began to fight bitterly. The battle was long and bloody, for the beasts were well matched, but finally, the red dragon was victorious, and the white dragon turned and fled.

Myrddin explained to Vortigern that the white dragon represented the Saxons, and the red dragon represented the Welsh, who in the fullness of time would reconquer their lands. It is said that this was how the Red Dragon became a symbol of Wales and how it found its way onto the Welsh flag.

Vortigern's fort was completed without futher misadventure. Myrddin then revealed his true identity to the King, telling him that he was Merlin, also known as Emrys. To show his gratitude, Vortigern named his newly built fort Dinas Emrys.

Reference: Beare, B. (1996) Wales - Myths and Legends. Parragon. Bristol, UK.