In Welsh Flint Castle is kown as Castell y Fflint. It is, predicatably, located in Flint, Flintshire, in North East Wales
Building work began in 1277 under Richard l'Engenour, who would later become Mayor of Chester4. The castle and its earthworks were built by 1,800 labourers and masons using locl Millstone Grit ashlar and sandstone.
In November 1280, the Savoyard master mason James of Saint George began overseeing construction at Flint for Edward I. He remained at the castle for 17 months. James of Saint George then moved onto Rhuddlan Castle to oversee its completion.
In 1182 Welsh forces under the command of Dafydd ap Gruffydd, brother of Llywelyn the Last besieged the castle in an attempted uprising against the English Crown.
When work ceased in 1286, Flint Castle had an inner ward and an outer bailey. They were separated by a tidal moat and connected by a gatehouse and drawbridge. A plantation town had also been laid out beyond the outer bailey. The inner ward had three large towers and a detached keep. This isolated tower protected the inner gatehouse and outer bailey. In total expenditure, Edward I spent £6068.7.5d creating both fortress and town.
In 1294 Flint was attacked again during the revolt of Madog ap Llywelyn; the constable of the castle was forced to set fire to the fortress to prevent its capture by the Welsh. The castle was later repaired and rebuilt.
With the conclusion to the Welsh Wars, English settlers and merchants were given property titles in the new town laid out in front of the castle. This plantation borough was protected by a defensive ditch with a wooden palisade on earth banking. Its outline remains visible in streets patterns.
In 1399 Richard II of England was held at Flint Castle by Henry Bolingbroke at Flint before being returned to London.
Sited on the western shore of the River Dee estuary, Flint Castle could be supplied by river or sea. Its harbour was protected by a defensive wall. Before the river's course was drastically changed in the 18th century, passage across the estuary at this point could be made directly by boat at high tide or by fording at low tide. The castle lies opposite to the English shore and Shotwick Castle in England.
The castle is based on medieval Savoyard models where one of the corner towers is enlarged and isolated. This independent structure served as both corner tower and keep or donjon, as at Dourdan, France. Flint's keep has been compared to the donjon at Aigues-Mortes in France. Edward I would have been familiar with Aigues-Mortes having passed through the fortress on the way to join the Eighth Crusade in 1270. On the other hand the idea might have come frome James of Saint George, who came from savoy.
The keep is an impressive structure. Its stone walls are 7 metres (23 ft) thick at the base and 5 metres (16 ft) above. Access was gained by crossing a drawbridge into a central entrance chamber on the first floor. Originally there would have been at one more storey. Upper floors had small rooms built into the thick walls. A timber gallery was built on top of the keep for the visit of Edward, Prince of Wales in 1301. On the ground floor is a vaulted passage that runs all the way around the inside of the keep.
Flint's design was not repeated in any other castle built by Edward I in North Wales, and remains unique within the British Isles.
By the 19th century part of the site's outer bailey was used as Flintshire's County Jail. A quarry also operated nearby.