The dragon was not the red wyvern that would later become Wales's flag. It was Uther Pendragon's standard, lifted from the legendary chronicles of Geoffrey of Monmouth and Nennius. Glyndwr was a literate man steeped in the old British histories, and at this stage of his revolt he reached for myth as freely as he reached for steel. His letters that year to the kings of Scotland and Ireland brimmed with the same vocabulary - prophecy, Merlin, the old British inheritance about to be reclaimed. The golden dragon over Tuthill was a declaration, not a tactical flag. Within a few years he would put it down and adopt instead the four lions of the House of Gwynedd, the plainer arms of the last native princes. Pragmatism was catching up with prophecy.

Almost nothing of the battle itself survives in writing. The only contemporary account comes from Adam of Usk, a Welsh-born cleric travelling through troubled times, who summarised the day in a single brisk Latin sentence. Glyndwr intended to lay siege to Caernarvon. He raised his standard. The garrison sallied out. Three hundred of his men were killed, and he was driven off. That is the whole record. The site itself, a low rise called Tuthill just outside the medieval town walls, is now buried under modern Caernarfon - housing, a school, a quiet residential street. There is no marker, no obvious slope to identify. The dead vanished into the ground beneath what is now suburban Gwynedd.

By the cold arithmetic of battle, Tuthill was a defeat. By the longer arithmetic of revolt, it was something else. The very fact that Glyndwr could march openly on the largest royal castle in north Wales, in broad daylight on a feast day, showed that the rebellion had teeth. Edward I had built Caernarfon to prove that English power was permanent in Gwynedd. Seeing a Welsh army gathered beneath its walls - even briefly, even unsuccessfully - undid some of that proof. Within three years Glyndwr held most of Wales, summoned parliaments at Machynlleth, and corresponded as a sovereign prince with the kings of France and Scotland.

Caernarfon Castle did not surrender to Glyndwr. It held out through repeated sieges between 1401 and 1404, defended by a garrison sometimes reduced to a few dozen men behind banded stone walls modelled, some scholars think, on the walls of Constantinople. The town was burned more than once. The castle never broke. By 1409, with English reinforcements pouring into Wales and the rebellion losing ground, Glyndwr himself disappeared from the historical record. No one is certain where or when he died. He was never captured, never executed, never displayed in a London cage. He simply walked out of view, leaving the golden dragon to be picked up centuries later by people who had heard the story and wanted it to mean something.