For the small seaside town of Deganwy, it’s strategic significance has been recognized since the early Middle Ages. Its position was fitting for military defense, with the massive volcanic rock around the region adding to the defense strategy. However, its location actually turned out to also be a weakness, as its positioning made it difficult to resupply the garrison when under siege.

Very little is known about the history of the castle. Researchers believe that Deganwy Castle was the royal court of Maelgwyn, the 6th century king of Gwynedd. The castle was severely damaged by lightning around the year 812 and was subsequently rebuilt, only to be destroyed by Saxon invaders a decade later. During the 11th century, a new castle was constructed on the orders of Robert of Rhuddlan, lord of North Wales.

Now in the hands of Wales, the castle became the base of Llywelyn ap Iorwerth, Prince of Gwynedd, who aided King John until he turned against the crown in 1211. John sent his army to destroy Deganwy Castle, and two years later, Llywelyn returned and had it rebuilt. It was destroyed once again by the Welsh after Iorwerth death to prevent the English from repurposing it.

Between 1245 and 1254, Henry III rebuilt and re-fortified the castle, only to have it captured by the Welsh led by Prince Llywelyn ap Gruffydd. Henry III sealed the Treaty of Montgomery in 1267, recognizing Gruffydd as overlord of Wales. After his death, Edward I conquered Wales during the two Wars of Independence and the besieged castle.

Edward went on to start a large-scale castle-building program, however, Deganwy was completely abandoned and are seen in the ruins that remain today.