It seems probable that Pembrokeshire was one of the earliest Norman conquests in South Wales, as in 1073 and 1074 the _Brut_ tells of two expeditions of "the French" into Dyfed, a region which included not only what we now call Pembrokeshire, but also Strath Towy, which comprised an extensive district on both sides of the valley of the Towy.[898] The _Annales Cambriæ_ name Hugh de Montgomeri, Earl Roger's eldest son, in connection with the second of these expeditions, seven years before the expedition of King William into Wales in 1081.[899] The House of Montgomeri certainly took the most conspicuous part in the conquest of Dyfed and Cardigan, which was completed, according to the _Brut_, in 1093.[900] Arnulf of Montgomeri, fifth son of Earl Roger, was the leader of this conquest. But his father must at the same time have been operating in Cardigan, as the building of the castle of Cilgerran, which is on the very borders of Pembroke and Cardigan, is attributed to him. How far Earl Roger made himself master of Ceredigion it is impossible to say. Later writers say that he built the castle of Cardigan, but we have not been able to find any early authority for this statement, which in itself is not improbable. Powell's _History_ makes him do homage to William Rufus for the lordship of Cardigan, but here again the authority is doubtful.[901] The fact that a castle in or near Aberystwyth was not built until 1109 may indicate that the conquest of Northern Cardigan was not completed till it became the portion of the De Clares. This took place in 1109, when Henry I. deposed Cadwgan, a Welsh prince whom he had made Lord of Cardigan, and gave the lordship to Gilbert de Clare, who immediately proceeded to build the above-mentioned castle, and to restore Earl Roger's castle at Cilgerran (Dingeraint).[902] From this time the castle and district of Cardigan continued to be an appanage of the House of Clare (of course with frequent interruptions from Welsh invasions), and of the family of William Marshall, to whom the Clare lands came by marriage. The authority of these earls was suspended during the reign of Henry II., when he made Rhys ap Griffith, who had possessed himself of Ceredigion by conquest, Justiciar of South Wales, but in the reigns of John and Henry III., the _Close Rolls_ show that Cardigan Castle and county were generally in the hands of the Marshalls. The conquest of Pembrokeshire must have been closely followed by that of what is now Carmarthenshire, which was then reckoned as part of Dyfed.[903] We first hear of the castle of Rhyd y Gors in 1094,[904] but it evidently existed earlier. This castle we believe to have been the important castle of Carmarthen (see _post_). It was founded by William, son of Baldwin, sheriff of Devon, and cousin of the Gilbert de Clare who at a later period was made Lord of Cardigan by Henry I. We thus see at what an early date this important family made its appearance in Welsh history.