The present Denbigh Castle was built by Edward I after 1282 as a way to control the Welsh populace he’d just defeated.
The castle was built on the site of a Llys (or seat) of the Welsh Princes dating back several hundred years. Building the new Norman Castle on this site was a deliberate attempt to project the power of the King of England.
“Along with over half a mile of town walls, Denbigh Castle is a classic fortress of Edwardian proportions. Edward I’s successful 13th-century campaign in the region was cemented by the creation of an English borough in Denbigh from 1282 onwards. He simply built on top of what was a traditional Welsh stronghold. In so doing, he made sure all traces of Dafydd ap Gruffudd, the previous unlucky incumbent, were removed for ever.
Henry de Lacy, one of the King’s loyal commanders, was given control of the area and had the task of building the new castle. He couldn’t go far wrong with the king’s master mason, James of St George, at his side. It wasn’t all plain sailing however. A Welsh rebellion, led by Madog ap Llywelyn, captured the partly-built castle in 1294 but Edward’s dominance and the castle-building programme were soon restored. You can see for yourself the two phases of building work. The post-rebellion work is marked by different colour stone, thicker curtain walls and a hint of Caernarfon-style angular towers.” http://cadw.wales.gov.uk/daysout/denbighcastle/?lang=en