In 1405 Glyndwr’s forces met with a reverse at Monnow, where they attacked Prince Henry, and a battle was fought in which no quarter was given on either side, and again at Pwll Melyn, in Brecon, where fifteen hundred Welshmen fell, and among the slain was Owen’s brother.
The King, emboldened by these successes, himself marched against Owen, but Glyndwr was too cautious to risk another pitched battle, and Henry had to retire without having effected anything.
Little is known of Owen’s movements for some while, but his power was certainly on the decline. The King offered free pardon to all his adherents, excepting, however, Owen himself, and the Welsh wavered and many deserted him.
However, in 1407 he met with a notable though not far-reaching success.
Aberystwyth Castle was held for him, and Prince Henry determined to take it. At the head of a large force he invested the fortress, and was supplied with cannons sent from Yorkshire to Bristol, and thence transported by sea. Great stores of bows, arrows, stone shot, and sulphur were collected at Hereford. Woods on the banks of the Severn were cut down to furnish siege machinery, and a troop of carpenters was despatched from Bristol to erect scaffoldings and towers for the taking of the formidable castle. But all failed. The King’s particular cannon, weighing four and a half tons, that was discharged once in the hour, and made great noise but did little harm, did not frighten the besieged into surrender.
Prince Henry found the castle impregnable, and sat down before it to reduce it by starvation. Provisions began to fail within, and Glyndwr’s commander, Rhys ab Gruffydd, was constrained to open negotiations with the besiegers. It was agreed that unless the fortress were relieved by All Saints’ Day (November 1st) the Welsh garrison should surrender.
So confident was the Prince that Glyndwr could not throw any force into it, that he left Wales, and only an inconsiderable portion of his army remained to watch the castle.
Owen seized his opportunity, slipped unexpectedly into Aberystwyth with fresh forces, and defied the English once more.
In 1408 Owen’s dearly loved and faithful wife and Sir Edmund Mortimer’s children fell into the King’s hands when he captured Harlech, and they were sent to London.
Owen’s fortunes dwindled more and more; he was accompanied by a small band only, and was engaged in a guerilla warfare alone. What eventually became of him is unknown. It was said that finally, deserted by all, he wandered about the country in the disguise of a shepherd. It is supposed, with some good reason, that he found a refuge in the house of his married daughter at Monnington.