John Thomas was a labourer's son from Cellan, Ceredigion. In 1853 he moved to Liverpool to work in a draper's shop. Over a period of ten years the work had a detrimental effect on his health and he was forced to find employment in the open air. Therefore, at the beginning of the 1860s, he became a traveller for a firm dealing in writing materials and photographs of famous people. At that time publishing and selling small photographs of celebrities (carte-de-visite photographs) was a very lucrative business. When he realised how few of the photographs he had to sell were of Welsh celebrities he undertook to change things himself.
He learnt the rudiments of photography and in 1863 he began taking photographs of the famous by inviting a number of well-known preachers to sit for their portraits. The enterprise was a success and by 1867 he was confident enough to establish his own photographic business, The Cambrian Gallery. He worked as a photographer for about forty years, and during that time he travelled widely in north, mid and south Wales taking photographs of landscapes as well as people.
When he retired from business a collection of over three thousand of his negatives was bought by Sir O M Edwards to illustrate the magazine Cymru. John Thomas had worked with OM for many years by supplying him with illustrations and articles for the magazine. OM paid the following tribute to him for help in illustrating the magazine, "... you can well understand my joy in receiving an offer of help from Mr John Thomas, in his own modest style. I knew that no-one has such a complete collection of views of Welsh historic sites. Whenever he visits a particular area, he adds to his collection the picturesque, famous or unusual that he finds there. His rich gallery has been made available to me to use with the warmest of welcomes... It is good to know that the Cambrian Gallery contains a collection of views from nearly every part of Wales, and of the characters who lived in those parts in recent years." (Translated from Welsh, Cymru 17 (1899), p.134)
John Thomas died in October 1905.
Today the negatives which O M Edwards bought from John Thomas form part of the photographic collection of the National Library of Wales.