The red dragon has enjoyed an association with Wales for hundreds of years. The later Roman cavalry was the primary defending force against the Saxons towards the end of the occupation.
With the invasions of the Angles and Saxons, the Britons were driven back towards Wales. By the seventh century ... It was the beginning of the flag as we know it today.
The standard bears a marked similarity to the arms of Llewelyn ap Gruffydd, the flag of the royal house of Gwynedd. Llewelyn was the last prince of Wales prior to its conquest by Edward I.