Peter Williams, 1773

In the 1560s a theological division between John Calvin and Jacobus Arminius set reverberations in the then nascent Protestantism that have continued to echo through history. (They didn't meet: Calvin died in 1564 when Arminius was just four years old.) 

Simplistically, Calvin taught that God had predetermined the spiritual destination - whether to heaven or to hell - of every person (Wiki). Arminius taught that Calvin's view 'made God the author of evil'. He asserted, to the contrary, that God gave people a choice between damnation and salvation. (Wiki). 

By the time of our putative heretic these twin tracks had cut deep grooves in church history. Charles Wesley, the Methodist leader, was firmly Arminian with his evangelical emphasis on individual choice. 

In 1745 Peter Williams was ordained deacon in the Church of England (which then encompassed Wales). He served as curate in Eglwys Gymyn, Swansea, Llangrannog, and Llandysilio Gogo. His affinity with Methodism meant that his bishop refused to ordain him as a priest. (A fuller and entertaining account of William's life is here.)

Two years later Williams formally became a Methodist and toured Wales as an itinerant preacher. He married Mary Jenkins of Llanlluan the following year and they settled at Gelli Lednais, Llandyfaelog [wiki]. He wrote hymns and books and translated a number of works from English into Welsh. 

In 1770, aged 47, Williams published an edition of the Welsh Bible with marginal references and explanatory notes.  (Testament Newydd ein harglwydd a'n hiachawdwr Iesu Grist. Publisher: Argraffwyd dros y Parchedig Mr. Peter Williams, gan Ioan Ross, Caerfyrddin.) It was immediately popular and frequently reprinted. 

In 1773  he published Mynegir Ysgrythurol which, it was claimed, was "the first commentary on the Bible ever published in the Welsh language" and it too was very popular. 

However, some of those who examined his commentary convinced themselves that the work was heretical. A marginal note on John Chapter 1, verse 1, "in the opinion of some persons in the connexion, amounted to Sabellianism." (Blurring or erasing the differences between the Persons of the Trinity.) (Rees, p. 385)

Peter Williams had had two staunch and respected defenders within Methodism, a Mr Rowlands and a Mr Williams of Pantycelyn. However in 1791, after they had died, "Peter Williams was unceremoniously expelled from the connexion."  (Protestant Nonconformity in Wales, p26) I have found no details of his expulsion nor how it was done. He was then aged 69 and the dispute "continued to disturb the peace of that [Methodist] body for above twenty years." (Rees, p385.) 

Williams was not without friends, however, and the pulpits of "the more rigidly orthodox Independents and Antipaedobaptists were cheerfully opened to him." (ibid.) He could feel vindicated by their welcome.

(Sources: Thomas Rees, History of Protestant Nonconformity in Wales, from its rise to the present time. London, Pp. vii. 512. J. Snow, 1861 [here], Dictionary of Welsh Biography, Image wikicommons.)