In terms of the Norman settlements in Wales, the major consequence of the conflict between Henry I and the rulers of Powys was the introduction towest Wales of one family, the Clares, which was to play a major role in the history of the southern marchlands. Gilbert fitz Richard was alreadylord of Clare in Tonbridge; he and his family had grown rich in England. Gilbert had frequently asked the king for land in Wales, indicating thatthere were rich pickings in Wales even for the most powerful Norman families. Exasperated with fighting with Cadwgan and his kin, Henry determinedthat one part of their territory should be made safe in the hands of an immigrant lord. In a famous phrase, Henry said to Gilbert "Now I will giveyou the lands of Cadwgan ap Bleddyn. Go and take possession of it." Gilbert was given an area with one major castle at Cardigan already in use, butwith the hinterland little explored. He secured Cardigan and established himself at Aberystwyth (not the later Edwardian stronghold) andcommissioned a number of castles, some of which bore or came to bear Welsh names, while others were identified by the name of their FrenchCastellans (Walker 1990). They included:

* Walter's Castle
* Razo's Castle
* Lampeter Castle, aka Stephen's Castle: King Stephen built a motte castle here in 1137, now on the grounds of the college.
* Humphrey's Castle (later rebuilt as Castell Hywel)
* Richard's Castle
* Blaenporth, aka Ralph's Castle: A minor Norman motte-and-bailey taken and destroyed by the Welsh in 1215.

Gilbert's eldest son Richard de Clare was killed in an ambush as he travelled through Abergavenny and Brecknock on his way to Ceredigion in 1136.Richard's youngest son Roger, who succeeded his father as earl in 1152, also campaigned in Wales and either built or reconditioned a number ofstrategic castles, including:

* Castell Hywel: Between Lampeter & Newcastle Emlyn. Destroyed by the Welsh in 1136 and rebuilt in 1153.
* Aberdyfi (Aberdovey)
* Dineirth: A motte-and-bailey castle near Aberystwyth destroyed in 1208. Some signs of masonry.
* Llanrhystud

Most of the castles above have long since disappeared from the landscape, however, another branch of the de Clare family (the junior branch) was toleave an even more indelible mark on castle building in Wales. Indeed, many claim that Gilbert de Clare's masterpiece at Caerphilly represents amajor turning point in castle design and construction in Britain.