Marion has worked for Oxfam GB since 1995, first in Angola and then in Oxford, where she leads the Public Health Promotion Team, focusing on community mobilisation and health and hygiene promotion in humanitarian crises.

Marion has worked in community and public health in relief and development programmes in the UK, Africa, the Middle East, Asia and Latin America and is the co-author of two books: Hygiene Promotion: A Practical Manual for Relief and Development and Humanitarian Programmes and HIV and AIDS: A Practical Approach to Mainstreaming.