John Griffith was among the most prominent clergymen in industrial south Wales during the second half of the nineteenth century. He was rector of Aberdare from 1846 until 1859. From 1859 until his death in 1885 he was vicar of Merthyr Tydfil where he proved a strong supporter of workers' rights and, by the end of his life a supporter of the disestablishment of the Church of England in Wales. This reflected the way in which he gradually abandoned the strong Tory principles that he espoused at the beginning of his career at Aberdare. He died on 24 April 1885.