David started his academic career studying zoology in the University of Wales, successively in Swansea, Bangor and Cardiff as undergrad, post-grad and post-doc. He was then recruited by Andrew McLean and Geoff Dolphin to join the National Radiological Protection Board at its inception in 1971. David's subsequent career has been spent in radiological protection until his retirement in 2008. Throughout that time in NRPB, Health Protection Agency, and Public Health England, his main interest has been the development and application of chromosomal aberration analysis as a biological dosemeter for investigating radiation accidents. He has been instrumental in steering the evolution of this field from a promising research idea into a routine component of the radiological protection programmes of many countries. From this very practical application arose a large body of dose response data, particularly at low doses, which has additionally provided an ideal endpoint for testing many of the more fundamental concepts in radiobiology such as the dose rate effect, the RBE/LET relationship and so on. A significant point in his career was the 1986 Chernobyl accident, followed soon after by the break-up of the Soviet Union. These paved the way for him to develop highly productive and enduring associations with a number of eastern laboratories. Latterly, with the heightened concerns for international terrorism, his work has turned to how the biological dosimetry community world-wide can mount a concerted and effectively response to mass casualty events involving radiation. In 'retirement' he maintains an active emeritus position with PHE and also has advisory roles with United Nations agencies, IAEA and WHO, in developing and optimising their rapid response preparedness.