A settlement has existed on this site from at least the beginning of the 6th century, when the poet Aneurin wrote of ‘the white houses of Glamorgan’ when referring to Llantrisant. It was seized around 1246 by Richard de Clare who built Llantrisant Castle. It is thought that de Clare established the borough of Llantrisant though the exact charter occurred in 1346.
In 1346, Llantrisant was granted a Royal Charter months before the archers from the town helped Edward, the Black Prince, win a victory against the French army at the Battle of Crecy. The Llantrisant longbow men were pivotal in the adoption of the English longbow as the missile weapon of choice for the English crown during the Middle Ages.
Tales of courageous longbowmen from the town, fighting at the Battle of Crecy under Lord of Glamorgan Hugh le Despenser, resulted in academics believing that was the reason behind those brave soldiers being rewarded with the issue of such a significant document. Sadly, the legend isn’t true, because the charter was actually presented five months earlier, on March 4, 1346. However, it is always comforting to imagine those gallant veterans of Crecy may have been the first to be bestowed with the freedom of the new Ancient Borough of Llantrisant on their return from victory. The charter was reissued in 1424 and gave those Burgesses, or Freemen, absolute possession of the land, the equivalent of the freehold tenure we have today, and made it clear that non-Burgesses could not trade in the town without paying for the privilege. Therefore, a free borough, or corporation town, was a community of Freemen and its main purpose was to earn a corporate living (Llantrisant.net).
Llantrisant was one of the eight boroughs constituting the Glamorgan borough following the Act of Union, a status it held until 1918.