Several Black Welsh individuals are recorded as living in Wales before Ystumllyn, mainly employed as servants and musicians to landowners and the aristocracy, following the vogue in Britain.

Welsh historian David Morris has identified 29 black people in South Wales parish registers between 1687 and 1814, including a horn player of Erddig whose master had his portrait painted.

Ystumllyn's biographer, Andrew Green, speculates that yet "more remain to be discovered" in North Wales, even if "their absolute numbers were small".

[1] Despite this, Ystumllyn has been described as the first black person of North Wales "about whom we have detailed knowledge" by Green, writing for the Oxford Dictionary of National Biography.

[1] The earliest is a small oil painting on wood produced by an unknown artisan artist, with a date and identification at the foot: "John Ystymllyn, 11 May 1754".

In 1999, it was made a Grade II listed building "as of special interest in commemorating a slave in service in Wales in the later years of the C18 [18th-century], who must have been well enough thought of that he was provided with a handsome memorial".

It bears a bleak, biographical englyn, composed by the Penrhyndeudraeth musician and poet Dafydd Siôn Siâms (1743–1831):[1][4][2][5]: 7 Yn India gynna'm ganwyd a nghamrau Yng Nghymru'm bedyddiwyd Wele'r fan dan lechan lwyd Du oeraidd y'm daearwyd.

Jones collated various oral traditions about the gardener that had passed down through his family, largely from his grandfather who had been Ystumllyn's doctor near the end of his life.

[7] Green has acknowledged the inadequacies of Jones' work, often "prone to variation, embroidery and forgetfulness", but it remains, in his view, "the most informative" and "frank" source for Ystumllyn's life.

[6] Robert Isaac Jones begins his account of Ystumllyn's life, admitting his uncertain origins, and tracing three narratives of his arrival in Wales.

[4] The third account, from John himself, asserted that he was captured by white men while "on the banks of a stream amid woodland attempting to catch a moorhen", and was abducted and taken to their ship to the "frightful howls" of his mother.

One unmarried maid from Hendre Mur, Trawsfynydd, Margaret Gruffydd, was tasked with bringing John "some bread, cheese and ale from the Plas".

When Margaret moved to her relatives' nearby mansion, Ynysgain Bach, Criccieth, for domestic work available there, Ystumllyn continued his courtship of her.

Near the end of his life, in "recognition for his service", Ellis Wynn gave Ystumllyn the house of "Y Nhyra Isa" or "Nanhyran", a small thatched cottage surrounded by a large, ancient garden.

[1] According to Ffion Mair Jones, these stories "portray a man of firm morals, who responded robustly to the preconceptions of his contemporaries about him as the only black person in the neighbourhood, and who adhered to the truth in any case of wrong committed against him or false step of his own".

[5]: 8  "Although the presence of a black man in Gwynedd inevitably aroused surprise and even shock", according to Green, "there's no suggestion that anyone held racist attitudes towards John".

This selection included Ystumllyn, who Ingram cited as "the most emblematic of the theme of this release", a man "whose settled life existence in rural Wales reminds us of the diversity of the historical experience of black people in Britain".

[13] In June 2020, an article about Ystumllyn was written in HortWeek[14] by Zehra Zaidi, a campaigner who set up We Too Built Britain to tell the stories of under-represented groups to show what we have in common (to then also be able to open up deeper conversations).

[18][19] The rose was mentioned in the House of Commons by Liz Saville Roberts, the Plaid Cymru MP for the area where Ystumllyn lived, in a request for a debate on black history stories.