John Meurig Thomas was bornon 15 December 1932 in Llanelli, Wales, the son of David John and Edyth Thomas. He was educated at Gwendraeth Grammar School (State Scholar), University College of Swansea (Hon. Fellow, 1985) and Queen Mary College, London. In 1959 he married (1st), Margaret Edwards (d 2002), having two daughters, and (2nd) in 2010, Professor Jehane Ragai, Cairo.

Having graduated with a BSc in Chemistry from Swansea in 1954, Thomas's career included: Scientific Officer, UK Atomic Energy Authority, 1957–58; Lecturer and Reader in Chemistry, UCNW, Bangor, 1958-69; Professor and Head of Department of Chemistry, UCW, Aberystwyth, 1969–78; Professor and Head of Department of Physical Chemistry, University of Cambridge, 1978–86; Director, Royal Institution, and Davy Faraday Research Laboratory, 1986–91; Resident Professor of Chemistry, 1986–88, Fullerian Professor of Chemistry, 1988–94, Professor of Chemistry, 1994–2002, Emeritus Professor, 2002, Royal Institution; Deputy Pro-Chancellor, University of Wales, 1991–94; Distinguished Research Fellow, Department of Materials Science and Metallurgy, University of Cambridge, 1993–2002; Master of Peterhouse College, Cambridge, 1993–2002.

He died on 13 November 2020.