[3] Even so, he had a lasting impact on Welsh culture, notably in founding the secret society known as the Gorsedd, through which Iolo Morganwg successfully co-opted the 18th-century Eisteddfod revival.

[4] Edward Williams was born in Pen-onn, near Llancarfan, Vale of Glamorgan, and raised in the village of Flemingston (or Flimston; Trefflemin in Welsh).

In Glamorgan, he took an interest in manuscript collection, and learnt to compose Welsh poetry from poets such as Lewis Hopkin, Rhys Morgan, and especially Siôn Bradford.

He produced a large number of manuscripts as evidence for his claims that ancient Druidic tradition had survived the Roman conquest, the conversion of the populace to Christianity, the persecution of bards under King Edward I, and other adversities.

[2] His success led him to return to London in 1791, where he founded the Gorsedd, a community of Welsh bards, at a ceremony on 21 June 1792 at Primrose Hill.

[7] Other works by Williams include the "Druid's Prayer", still used by the Gorsedd and by neo-Druid groups, a treatise on Welsh metrics called Cyfrinach Beirdd Ynys Prydain ("The Mystery of the Bards of the Isle of Britain"), published posthumously in 1828, and a hymn series published as Salmau yr Eglwys yn yr Anialwch ("Psalms of the church in the wilderness") in 1812.

The metaphysics elucidated in his forgeries and other works proposed a theory of concentric "rings of existence", proceeding outward from Annwn (the Otherworld) through Abred and Ceugant to Gwynfyd (purity or Heaven).

Towards the end of the 19th century, the grammarian Sir John Morris-Jones was involved in exposing Iolo as a forger, which led to the bard being labelled a charlatan.

[citation needed] It has been suggested that some of Iolo's claims were supported by oral tradition: recent research has revealed that the tale of Ieuan Gethin, a soldier in the Glyndŵr revolt, might have basis in fact.

[14] It reads: This stone was placed here by the East And Mid-Glamorgan sections of the National Union of Welsh Language Societies on the centenary of his death on 17/12/1826 to mark the house in which he sold books.A memorial plaque was erected in 2009, on the approximate site of the first Gorsedd ceremony, held on London's Primrose Hill in 1792,[15] and another memorial stone on Stalling Down near Cowbridge, where the first Gorsedd ceremony in Wales took place in 1795.

[17] A Welsh-language school in Cowbridge, Ysgol Iolo Morganwg, is named after him, and Super Furry Animals vocalist Gruff Rhys dedicated a song to him on his 2014 album, American Interior.