The King remained in the region of Rhuddlan until about the Feast of All Saints, and in the meantime the lord John, Archbishop of Canterbury, was sent to Llewellyn at Snowdon to treat for peace with him, or rather to advise and induce him to observe the peace which he had previously made with the King, and confirmed in writing and by oath, especially since the conditions had been carried out. But his mission was fruitless, for Llewellyn could not be induced to make peace. While the Archbishop delayed for three days in Snowdon, the English nobles, showing more foolishness than courage, secretly entered Snowdon, thinking that by craft they could seize it by their own unaided strength. But the Welsh, forewarned of their approach, advanced in force against them, and joining battle, easily prevailed over the small detachment of nobles and put them to flight. The fugitives thought to save themselves by crossing a certain river, but, owing to ignorance of the force of the current, several were drowned, namely, Luke de Tani, William de Dodingsele, William la Zouche, and others; the rest escaped with difficulty. This happened on the Festival of S. Leonard. When the Archbishop came down from Snowdon without accomplishing his aim, he uttered sentence of excommunication against Llewellyn as a violator of his oath, and a perjurer, and against David, his brother, and all their accomplices and abettors. About the same time died the lord Roger Mortimer, one of the most famous men of his age, and a valiant soldier. On his death, the lord Edmund, his eldest son and heir, together with his brother--perchance, as is believed, to appease the King--laid an ambush for the said Llewellyn; for, being informed of his movements by spies, the said Edmund gathered together a large and powerful force, and, more by chance than was imagined at that time, fell in with Llewellyn when he had descended from the mountains of Snowdon for some unknown reason and was traversing the lower ground with the few followers who still adhered to him, and put him, and those of his men who were unable to escape, to death by the sword. The head of the Prince, whom he recognized among the slain, he cut off and sent to the lord King. This memorable triumph of the slaying of Llewellyn happened, under God, about the Feast of S. Thomas the Apostle, before Christmas. The King, glorying in his victory, ordered the head to be taken to London, and affixed it to the Tower on a spear as a memorial of so notable a success.