| 1966-1969 | Scientific Officer, Rutherford Laboratory, Chilton, Oxon, U.K. |
| 1969-1971 | Fellow, CERN, Geneva, Switzerland. |
| 1971-1974 | Staff member, CERN, Geneva, Switzerland. |
| 1974-2009 | Professor of Theoretical Physics, University of Liverpool. |
| 2009- | Emeritus Professor, University of Liverpool. |
| 1980- | Fellow of the Institute of Physics. |
| 1983-1988 | Head of DAMTP, University of Liverpool. |
| 2003-2007 | PPARC Senior Fellowship. |
| 2023- | Fellow Learned Society of Wales. |
| 1969 | University of Wisconsin, Madison, USA. |
| 1972 | Cal. Inst. Tech., Pasadena, USA. |
| 1979 | University of Wisconsin, Madison, USA. |
| 1985/6 | University of Illinois, Urbana, USA. |
| 1986 | CERN, Geneva, Switzerland. |
| 2000 | Jefferson Lab., Newport News, USA, |