No one knows precisely who built the original wooden Skenfrith Castle on the bank of the River Monnow. The fortress was of typical Norman motte and bailey construction, so it was most likely begun by one of the many Norman generals who received parcels of land from William the Conqueror after 1066.
In approximately 1136, King Stephen established the Honour of Grosmont, also called the lordship of the Trilateral or the Three Castles. This lordship, given to Payn FitzJohn, included the area of Skenfrith Castle as well as two other castles, Grosmont and White. All three were located near the border of Wales and England, along an important route for travellers, the Monmouth Valley. Skenfrith was the only one built in a low-lying area.
Payn Fitz John returned the Honour of Grosmont to King Stephen in exchange for a province called Archenfield. He did not have much time to enjoy his new province, however, because he died soon after. In 1187, King Henry II commanded the engineer, Ralph Grosmont, to rebuild Skenfrith Castle out of stone.
Grosmont completed the eastern wall and part of the north-eastern tower, but the project was cancelled in 1188. In 1193, the Sheriff of the area, William Braose, decided to use the unfinished castle anyway, and fortified it with a wooden palisade.
Hubert de Burgh received the Honour of Grosmont in 1219, and he immediately set to work rebuilding Skenfrith Castle with stone. Work proceeded quickly, but in 1220 the River Monnow flooded and destroyed most of the previous work. De Burgh filled in the old castle and levelled the area, thereby raising the height of the ground to prevent repeated flooding. He then constructed a new stone castle on the site of the old one.
In 1239 King Henry III took over the Trilateral. He ordered the addition of a lead roof to the round keep of Skenfrith Castle. Prince Edward (later Edward I) owned the Three Castles from 1254 – 1267, and he probably built the fifth tower at Skenfrith, a D-shaped tower set into the more vulnerable western wall. In 1267 Henry III gave Skenfrith and the other two castles to his second son, Prince Edmund “Crouchback”, Earl of Lancaster.
The Lancaster family maintained the Three Castles, including Skenfrith, for the next two centuries, but only Grosmont was used as a residence. By the 16th century, Skenfrith and its two sister castles, Grosmont and White, had been abandoned and were falling into ruin.
Skenfrith Castle almost disappeared from history at that time. It passed through several hands, including those of Henry IV, the Dukes of Lancaster, and the Dukes of Beaufort, until it was finally given to the National Trust. Today, Skenfrith, along with Grosmont and White Castle, is conserved by Cadw, the Welsh historical agency.