Thomas was born in Cwmbran, Monmouthshire; his father A.E. Thomas, was working class.Matthew Saunders, "Ivor Bulmer-Thomas" (Obituary), The Independent, 8 October 1993. He went to West Monmouth School in Pontypool, where he abandoned his father's Baptist faith in favour of the Anglo-Catholic wing of the Church of England,"Ivor Bulmer-Thomas" (Obituary), The Times, 8 October 1993. a decision that was to affect his future career profoundly. Although a pious believer, his personal piety was described by Robin Denniston in his Guardian obituary as "always gentle and humble".Robin Denniston, "Dissenter in the Pews: Ivor Bulmer-Thomas" (Obituary), The Guardian, 9 October 1993.
