Monstrous erections

 

In September 1267, at the ford of Montgomery (Rhyd Chwima), Prince Llywelyn ap Gruffudd knelt before Henry III and swore the double oath of homage and fealty. The treaty left Llywelyn in possession of much of Wales along the border from Chester to Abergavenny, and gained him formal recognition of his title. In exchange he and his heirs were made perpetual vassals of the English crown, and he agreed to pay a mortgage of 25,000 marks (about £20,000 in English sterling) at set rates per annum. 

To really understand what followed, we have to look at what the treaty did not say. There is no mention in the text of the lordship of Glamorgan, which remained intact in the hands of its lord Gilbert de Clare, earl of Gloucester. 

Gilbert had succeeded his father, Richard, as earl in 1264. He pursued a vacillating course in the Montfortian wars in England, changing sides as it suited his interest. In 1267, before he marched on London, Gilbert came to agreement with Llywelyn: according to Brut y Tywysogion, the attack on London was a joint enterprise between the two men, and Gilbert raised his army in Wales. Hence, when he seized the capital in the summer of that year, London was effectively conquered by an army of Welshmen. Before anyone gets too excited, bear in mind they were led by an English earl. 

The following year, October 1268, Gilbert and Llywelyn met again, this time in Cantref Selyf in Brycheiniog. The text of their treaty survives (attached, third pic), and is arguably just as significant as the better-known treaty of Montgomery. The Cantref Selyf agreement shows the state of play in Glamorgan at this time. When Gilbert switched sides to join the king, in 1265, Llywelyn seized the opportunity to invade the lordship. According to the treaty, he had pushed on from the valley of the Usk and gained effective control of Northern Miskin as far as Pontypridd and Senghenydd above Caeach. There is no other record of Llywelyn's conquests in northern Glamorgan, but the Cantref Selyf agreement is sufficient proof. This was a serious bit of diplomacy, and neither Llywelyn or his rival were messing about. 

Both men were anxious to prevent their dispute being transferred to the ging's court (Coram Rege). This would take the final judgement out of their hands and into those of royal justices, which had to be avoided at all costs. Hence they reached a compromise: the men of Miskin and Senhenydd, who had been withdrawn to Llywelyn's lordship, would remain in his possession along with their goods and chattels. Otherwise the status quo would be maintained in the Glamorgan uplands, and neither party would wage war on the other.

Gilbert had already thought of an insurance policy. In April 1268, several months before the meeting at Cantref Selyf, he started work on the mighty fortress of Caerphilly. As JE Lloyd remarked, the terms of the treaty make the story of Caerphilly 'clear as day'. The Welsh prince had advanced deep into southern Glamorgan, so Gilbert's monstrous erection was intended to guard Cardiff and the coast lands. Llywelyn, for his part, was just as determined to knock it over.