During the revolt at the beginning of the fifteenth century, Hywel Selau sided with Henry IV instead of his cousin, Owain Glyndwr. As a result, Nannau was razed to the ground during the early stages of the revolt. According to tradition, Hywel Selau himself was put to death on Nannau land by Owain’s supporters in 1402 and his body was left in a hollow tree nearby. The tree was afterwards known as ‘Glyndwr’s Oak’... 2
"...Nannau was formerly possessed by a Welsh knight named Howell Sele, who, refusing to take part with Owen Glendwr when he rose to assert his rights against Henry the Fourth, incurred the enmity of the aspirant to the sovereignty of Wales. Glendwr, whose residence was not far from this part of the country, and to whom, indeed, much of the valley which extends from Dolgelley to Llangollen, and is called Glendwrdwy, belonged, on one occasion resolved to take 'his pleasure in the woods' of Howell Sele; and, without seeking permission or caring for opposition, set out accompanied by his friend Madog, and made the glades of Nannau re-echo to the sound of their horns. The unaccustomed blast was heard by Howell, and his anger arose: he armed himself, seized his sword, and hurrying forth, placed himself in a spot where he knew the intruders must pass. It was not long before the proud Owen and his companion came in sight; and there, beneath an oak of gigantic size, and already hollow with age, although green and flourishing, they saw the frowning chieftan, who asked in a loud and severe voice how Glendwr, a rebel to his king, a disturber of the peace of his country, presumed to enter his grounds and hunt without his leave. A fierce answer was of course returned, and the quarrel which both sought was soon too deadly to be decided by any other means than the sword. The fought long and furiously,with none to witness the affray but Madog, who stood by. The advantage was with Glendwr, and Howell Sele was slain. A fearful pause ensued. The master killed in his own woods; his known enemy having been seen on his way to the fatal hunting scene: these facts were too glaring to be concealed—Glendwr's conscience told him he had done amiss, and he dared not stand the brunt of an inquiry. Aided by his friend to took his measures accordingly, and they both rode as swiftly as they could from the scene. All was desolate in the halls of Nannau; the master had disappeared and was nowhere to be found; the country had been searched far and near, but no trace of him was discovered. An infant heir was shewn by the weeping mother to his dejected followers; and Howell Sele was mourned for several years, and his fate unaccounted for. The great attempt of Owen Glendwr had failed. Hotspur had fallen at the battle of Shrewsbury; while the chief who was his ally had looked on in safety on the other side of the river. Henry the Fourth and his victorious son were crowned with conquest, and the Welsh prince had found an obscure grave. The lady of Nannau still wept her lord; but still, with the tenacity of affection, she trusted that he might yet return; and her vows at the altar of St. Mary were, that she might yet behold him once more. One dark November night, when the wind howled fearfully among the pine-woods, which waved gloomily round the deserted mansion, and all the household were preparing for repose, a knight urged his steed up the steep mountain-road that leads from the brawling torrent of the Mawddach to the heights now enveloped in mist, and pausing at the portal, sounded the horn which hung at the castle-gate. He demanded to see the lady of Nannau on pressing business which would brook no delay, and was conducted to her presence. The stranger paused a moment at the threshold, and then said, 'Summon all your household, lady, and let them be witnesses of the words I have to utter. I am Madog, the friend of the unfortunate Prince Owen Glendwr, who slew your husband.' He then went on to relate the circumstances of Howell Sele's death, and bade them search in the hollow of the oak for the body. No time was lost; all hurried to the spot, and there, enclosed in the huge trunk of the tree, was found the skeleton of their master with his armour on, and the sword still grasped in his bony hand. A magnificent tomb was erected for Howell Sele in the abbey of Kymmer, in the vale below, and the perpetual masses instituted for the repose of his soul; but from that time the oak of Nannau, which was standing thirty years since, was well known to be haunted with the evil spirits which that bad deed of Glendwr's had attracted." 3
"When Owen Glendower instituted his famous rebellion, Howard Sele (his cousin) refused to join, which enraged Owen to so great an extent that meeting him one day whilst hunting in Nannau Park, Owen having one attendant, Madog, they fell upon him and slew him, throwing his body into a great oak, hollow through age. This Nannau oak was for centuries an object of superstition... and fell down on 13th July, 1813. Throughout Merionethshire it was known as the Spirit's Blasted Tree—"Conbren Yr Ellyll." The vassals of Nannau, and Howell Sele's family were filled with alarm at his disappearance, but inquiries and searches gave no information of his whereabouts.
After Glendower's death, however, on a dark evening in November, an armed horseman was observed riding furiously up the hill which leads from Dolgelly to Nannau; it was Madog, who, after the death of Glendower, hastened to fulfill his master's last command and unravel the horrid mystery. He told the story and referred to the oak for confirmation.
The tree was cut into and Howell's body discovered, grasping with his right hand his rusty sword. The remains were removed to the neighbouring monastery of Cymmer, where they were interred. After the oak fell the wood was made into a variety of utensils, and many engravings of the tree, framed with its wood, are to be found in Dolgelly.
The story has been woven into a very fine ballad by Mr. Warrington, printed in the notes to Marmion, by Scott." 4