In response to the rebellion, discriminatory penal laws were implemented against the Welsh people; this deepened civil unrest and significantly increased support for Glyndŵr across Wales.

Glyndŵr refused two royal pardons and retreated to the Welsh hills and mountains with his remaining forces, where he continued to resist English rule by using guerrilla warfare tactics, until his disappearance in 1415, when he was recorded to have died by one of his followers by Adam of Usk.

His father, Gruffydd Fychan II had a claim to be hereditary Prince of Powys Fadog and was the Baron of Glyndyfrdwy and Lord of Cynllaith Owain, who died around 1370,[1] leaving Glyndŵr's mother Elen ferch Tomas ap Llywelyn, a woman with an accent from Ceredigion (Deheubarth), a widow when he was still a boy.

In March 1387, Owain fought as a squire to Richard FitzAlan, 4th Earl of Arundel,[16] where he saw action in the English Channel at the defeat of a Franco-Spanish-Flemish fleet off the coast of Kent during the Battle of Margate.

Upon the death in late 1387 of his father-in-law, Sir David Hanmer, knighted earlier that same year by the then King of England, Richard II, Glyndŵr returned to Wales as executor of his estate.

Glyndŵr's opportunities were further limited by the death of Sir Gregory Sais in 1390 and the sidelining of FitzAlan, and he probably returned to his stable Welsh estates,[citation needed] living there quietly for ten years during his forties.

His neighbour, Baron Grey of Ruthin, had seized control of some land, for which Glyndŵr appealed to the English Parliament, however, Owain's petition for redress was ignored.

Hotspur won a battle at Cadair Idris two days later, but that was to be his final service for the King of England, as he retired his command as leader of the English troops after dealing with Glyndŵr.

[34] In June, Glyndŵr scored his first major victory in the field at Mynydd Hyddgen on Pumlumon, however, retaliation by Henry IV on Strata Florida Abbey was to follow in October that same year.

[32] Then, by autumn, Gwynedd and Ceredigion (which temporarily submitted to England for a pardon) and Powys adhered to the rising against the English rule by supporting the rebellion.

Glyndŵr offered to release Mortimer for a large ransom but, in sharp contrast to his attitude to de Grey, Henry IV refused to pay.

A Welsh army including a French contingent assimilated into forces mainly from Glamorgan and the Rhondda Valleys region commanded by Owain Glyndŵr, his senior general Rhys Gethin and Cadwgan, Lord of Glyn Rhondda, defeated a large English invasion force reputedly led by King Henry IV himself at the Battle of Stalling Down in Glamorgan.

Enguerrand de Monstrelet, a later chronicler gives an uncorroborated account of a march through Herefordshire and on into Worcestershire to Woodbury Hill, ten miles from Worcester.

[56] On 31 March 1406 Glyndŵr wrote a letter to be sent to Charles VI of France in St Peter ad Vincula church at Pennal, hence its naming after the location it was written at.

[57] Following this letter, senior churchmen and important members of society flocked to Glyndŵr's banner and English resistance was reduced to a few isolated castles, walled towns, and fortified manor houses.

Facsimile copies involving specialist ageing techniques and moulds of Glyndŵr's seal were created by the National Library of Wales and presented by the heritage minister Alun Ffred Jones to six Welsh institutions in 2009.

[58] The royal great seal from 1404 was given to Charles IV of France and contains images and Glyndŵr's title –[59] Latin: Owynus Dei Gratia Princeps Walliae – "Owain, by the grace of God, Prince of Wales".

Glyndwr referred to himself as the "Prince of Wales" and claimed his "right of inheritance" in these letters[60] In early 1405, the Welsh forces, who had until then won several easy victories, suffered a series of defeats.

[citation needed] Rather than focusing on punitive expeditions as favoured by his father, the young Prince Henry adopted a strategy of economic blockade.

By 1407, this strategy was beginning to bear fruit, and by 1408, the English regained Aberystwyth and then marched north Harlech Castle, which also surrendered during the cold winter into 1409.

[62] Glyndŵr managed to escape capture by disguising himself as an elderly man, sneaking out of the castle and slipping past the English military blockade in the darkness of the night.

[citation needed] Glyndŵr retreated to the Welsh wilderness with a band of loyal supporters; he refused to surrender and continued the war with guerrilla tactics such as launching sporadic raids and ambushes throughout Wales and the English borderlands.

[67][page needed] As late as 1414, there were rumours that the Herefordshire-based Lollard leader Sir John Oldcastle was communicating with Owain, and reinforcements were sent to the major castles in the north and south.

Francis Kilvert wrote in his diary that he saw the grave of "Owen Glendower" in the churchyard at Monnington on Wye "[h]ard by the church porch and on the western side of it ...

It is a flat stone of whitish-grey shaped like a rude obelisk figure, sunk deep into the ground in the middle of an oblong patch of earth from which the turf has been pared away, and, alas, smashed into several fragments.

[68][81] Upon Owain's disappearance and death, his eldest (oldest child with descendants) daughter Alice came to be known as the Lady of Glyndyfrdwy and Cynllaith, and heiress de jure of the Principalities of Powys, South Wales and Gwynedd.

During 1431, she successfully went to court in Meirionydd to regain her inheritance as the heiress of Sycarth in Glyndyfrdwy against John, Earl of Somerset, who had been granted Owain's forfeited lands by the King of England in 1400.

[87][88] Professor John Edward Lloyd said: "There is no evidence that Llywelyn had any daughter but Gwenllian, born in the last year of his life and after his death confined for the rest of her days as a nun of the order of Sempringham".

He was perceived as a folk hero awaiting a call to return and liberate his people in the classic Welsh mythical role – Y Mab Darogan ("The Foretold Son").

The myth was that one day after a thousand years of servitude under English rule, a 'Son of Prophecy' would return the Welsh people as rulers of the island of Great Britain.