In order to strengthen himself still further, and at the same time to erect a bulwark between him and England, Llewelyn cemented his alliance with the powerful lords of the Marches by giving one of his daughters in marriage to Reginald de Braose, and the other to Ralph Mortimer. This lady Gladys, who married Mortimer, became the ancestress of Elizabeth of York, the mother of Henry VIII. Thus in the veins of the greatest of the Tudors there flowed some of the blood of the ancient royal house of Cunedda.
In the next period of his reign, between 1215 and 1226, we find Llewelyn at war with the Marshalls, the able and warlike Earls of Pembroke. William Marshall was as able a statesman as Llewelyn himself. His aim was to put an end to the turmoil into which England had been plunged by the struggle between king and barons. He was in favour of the Charter; but at the same time it seemed to him that the supremacy of a king was to be preferred to the lawless self-seeking of the great earls. He believed that the welfare of England demanded the existence of a strong central Government; and in this he was unquestionably right. In truth, Marshall was striving to achieve in England the very same thing that Llewelyn had been striving to achieve in Wales. With the death of John, and the accession of the innocent and untried Henry III, the power of the barons began to decline. Unfortunately the great Marshall died in 1219; and a vigorous war broke out between his son and Llewelyn. After some years, however, the younger Marshall lost the favour of the king; and Llewelyn, always quick to adjust his policy to a changed situation, at once concluded an alliance with him. Against such an alliance nothing could stand in Wales. Every castle in the country, with the solitary exception of Carmarthen, fell into their hands, and the king's army was defeated in a great battle at Grosmont.
With the victory of Grosmont the period of Llewelyn's aggressive policy comes to an end. Henceforward he is on the defensive, feeling the on-coming of old age, and desiring above all things to render Wales secure against disintegration after his death. Llewelyn had read correctly the lesson of the past. He knew that, as soon as the strong hand of an able ruler had been removed, the fruits of his policy had been dissipated by his mediocre successors. What he now desired so ardently was to build a Welsh State upon foundations so secure that it would not be overthrown by incapacity on the part of its sovereign. The definite announcement of Llewelyn's policy of dependence upon England produced two parties in Wales, one of them antagonistic to such dependence, the other favourable to it. This ultimately proved to be the rock upon which the plan was wrecked; but it was not until after the death of Llewelyn that the failure of his policy became apparent. While he lived, his genius and his prestige were sufficient to compel the reluctant acquiescence even of those princes who most strongly disapproved of his policy. An agreement was made with the English king, whereby Wales was to preserve its independence, while its Prince acknowledged his dependence, in the feudal sense, upon England. There was to be perpetual peace between the two kingdoms; and Wales was to support England in all foreign wars.
Llewelyn's eldest son, Griffith, an able and energetic young man, who would naturally have inherited his father's throne, was strongly opposed to the policy which had been adopted. In his view Welsh independence ought to be absolute and complete; and no political dealings with England fought to be carried on at all except on a footing of equality. The young prince was consequently looked upon as the natural leader of the war party. With what reluctance we do not know, Llewelyn made up his mind that Griffith should not inherit his throne, but that it should go to Davydd, the younger of his sons, an effeminate and peace-loving boy. With this purpose in view the aged Prince summoned again the Council of Princes to meet, this time at the Cistercian abbey of Strata Florida. There Davydd was duly nominated, and the oaths of allegiance of all the assembled chieftains taken. This was in 1238; and two years later Llewelyn died, and was buried in the monastery of Aberconway.
In the brief intervals of peace which he had enjoyed in the course of his long and strong reign, Llewelyn had proved himself not unmindful of the things of the intellect and the spirit. The Cistercian monks found in him a warm friend. It was at their home of Strata Florida that he summoned the last of his councils; and it was at their home on the slopes of the Conway that he came to sleep his last sleep. While he was reigning, the mendicant Orders had also come to Wales for the first time; and they, likewise, especially the Franciscan Friars, found in him a sympathetic protector; and it was by his favour that they acquired their beautiful home at Llan Vaes in Anglesey. We have seen how he negotiated with the Pope. With the desire of the Welsh Church to be completely independent of Canterbury he was in full sympathy, although he never went so far as to lay claims to the power of appointing Welsh bishops. Like almost all the greater Welsh princes he delighted in music and poetry, and was a munificent patron of the bard and the minstrel.
In accordance with the decree of the Council Davydd ascended his father's throne, and set himself to walk the path marked out for him. But the task which the great Llewelyn had barely been able to accomplish was far beyond the strength of his less able and less popular son. His brother Griffith had already been suspected of harbouring disloyal thoughts and had been immured by his father in the castle of Criccieth. In 1241 Davydd went to Gloucester, one of the three cities at which the kings of England used regularly to meet their advisers in council, and there did homage to Henry III. Then his real troubles began. The extreme nationalists were determined to put an end to the policy of dependence; and in the person of the imprisoned Griffith they knew that they would find an able and enthusiastic champion. And not only was Davydd opposed by the Welsh diehards; he also found enemies in many of the border princes and barons, who resented the supremacy of Gwynedd. Griffith's wife Senena was free; and she was chosen by the party of opposition to go to the king and plead her husband's cause. Henry III was sufficiently crafty to discern the opportunity of maintaining a state of discord in Wales, by playing off the one brother against the other. He accordingly decreed that both Davydd and Griffith should come to court, and have their differences settled by Welsh law. It soon became obvious, however, that Henry was not to be trusted by either party. He marched towards Chester, and then commenced to negotiate with Davydd. The king's terms were accepted; and Davydd went with Henry to London, and again swore allegiance. Meanwhile Griffith had been set at liberty. But his liberty was of short duration. Henry imprisoned him in the Tower of London where, in 1244, he met his death while attempting to escape.
In the summer of 1245 Henry gathered together a large army, and marched against North Wales. Deganwy was reached, and a new castle built there. This was waste of valuable time, and ere the work was completed the king found that Davydd had secured powerful allies in the form of famine and winter storms. It was the same old story that could be told of so many of the English invasions of Wales in the Middle—a swift and irresistible advance in summer, a long halt, then the oncoming of winter followed by a retreat which very frequently became a rout. In the next year Davydd died, and was laid to rest in his father's grave at Aberconway, whither, some time later, the body of his brother Griffith was also brought.
With the death of Davydd a disputed succession again arose. The two most obvious claimants, since Davydd had left no children, were Griffith's two sons, Owen Goch and Llewelyn. But Ralph Mortimer also claimed the throne through his wife Gladys, daughter of Llewelyn the Great; and when he died a few months later he transmitted his claims to his son Roger. An entirely new candidate, however, appeared on the scene in the person of the young Prince Edward, son of Henry III and heir to the English throne. The claim was vague, resting upon the agreement come to between Senena on behalf of Griffith, and Henry. In effect all that was claimed by Edward was the territory held by Llewelyn ap Griffith, which comprised the four cantrefs between the Dee and the Conway—Rhos, Rhuvonig, Dyffryn Clwyd, and Tegeingl—and certain lands south of the Dovey; and these he obtained. In Gwynedd Owen and Llewelyn now became joint rulers; and when they had done homage to the English king, they remained unmolested. Llewelyn had inherited a large measure of his grandfather's ability and force of character; and owing to the possession of these qualities he soon began to take the lead in affairs. With high and low alike he was immensely popular. This roused the jealousy of his two brothers, Owen and Davydd, and they rose in revolt against him. But from the start Llewelyn proved himself a most capable soldier. The rebels were swiftly defeated; Davydd escaped, and fled to the English court; while Owen was imprisoned. By the end of the year 1255 Llewelyn was without a rival in the North.