He was born at the Harp Inn (now known as Hafod y Gân) in Llanfair Talhaearn, Denbighshire. He was probably apprenticed to and then working for the architect and Denbighshire County Surveyor Thomas Penson between 1830 and 1843. He then served with ecclesiastical architects in London, and was employed by Sir Joseph Paxton to oversee the building of the Crystal Palace. He came to prominence as a member of Cymdeithas y Cymreigyddion in London, and became its president in 1849.
Suffering from ill health, he returned to Wales in 1865 and in 1869 took his own life by shooting himself in his bedroom at the Harp Inn. He is buried under a yew tree at St Mary's church in Llanfair Talhaearn.
Talhaiarn lived in England and France, but wrote in the Welsh language. His works included well-known lyrics such as Bugeilio'r Gwenith Gwyn (Watching the Wheat), and Mae Robin yn Swil (Robin is Shy). Whilst his bardic name is derived in a conventional way from the place of his birth, it is likely also to refer to Talhaearn Tad Awen, a noted 6th-century Welsh poet.
Although he was accepted into Gorsedd y Beirdd in Bala in 1869, he is known to have failed several times to win the chair at the Eisteddfod. In 1849 at the Aberffraw eisteddfod he rose to his feet to contest the adjudication and defend his defeated awdl. In 1863 at the Swansea eisteddfod he held that the Nonconformist judges were biased against him as an Anglican.
John Thomas compiled a series of books called "Welsh Melodies with Welsh and English Poetry". It was a collaborative work with John Jones creating the Welsh words and Thomas Oliphant the artist and musician writing the English (which was often not a translation) and authored by John Thomas the Welsh composer and harpist. There were four volumes, the first two published in 1862, the third in 1870 and the fourth in 1874.
- Welsh Biography Online
- Hilling J B "The Historic Architecture of Wales", UWP, Cardiff 1976 225
- British Library