In order to assert his claim to be the most important of the Welsh princes, he felt the need to exercise his authority in the strategic area which is the Severn Valley, giving as it does access to the heartlands of Wales.

In order to consolidate his newly conquered lands and to affirm his control, Llywelyn ap Gruffydd constructed the castle at Dolforwyn between 1273 and 1277, for a recorded cost of £174 6s 8d.

An inventory taken at the time recites the rooms, which included an armoury in the round tower as well as domestic ranges with a pantry, buttery, kitchen, brewhouse, bakehouse, chapel, hall, a lady's chamber and two granges for the storage of grain.

The ownership of the castle passed to the Earls of Powis and was subsequently bought by the grandfather of the antiquarian John Davies Knatchbull Lloyd, who gave the site to the Welsh Ancient Monuments Board (now Cadw) in 1955.

[2][3] John Milton's 1634 masque Comus expanded this legend, with Sabrina saved by water nymphs, and made into the goddess of the river Severn.

[4] Bernard Cornwell, as part of The Warlord Chronicles, depicts Dolforwyn as a fictional iron age hillfort in his 1995 book The Winter King.

Finds from these excavations included part of a leather book cover, a small die, a silver coin from the reign of Edward II and a large array of spent stone catapult balls from the English siege of 1277.

These included a small stone lined hall, English repairs to Welsh masonry (shown by different types of mortar), a suspected wheat-drying oven and a 6 m (20 ft) cistern/cellar well (with indication it might be deeper).