Mary Tiffen read history at Cambridge University, but after a PhD at the London School of Economics, worked on agricultural development in Africa and the Middle East where her husband, Brian Tiffen, was working with the British Council. In 1983 she joined the Overseas Development Institute (ODI) in London, initially working on irrigation, and later on more general issues. She is best known as the leader of a team examining change during 1930–1990 in Machakos District, Kenya. The resulting book by Tiffen, Mortimore and Gichuki, More People, Less Erosion: Environmental Recovery in Kenya, helped change thinking on the relationship between population growth, poverty, and environmental degradation. Click here for more information. She retired from ODI in 1994, and in 1998 she and Michael Mortimore set up Drylands Research in Crewkerne, Somerset, to carry out studies in four African countries to test further the hypotheses arising out of the Machakos study. After a second retirement in 2002, she turned her attention to her own family history, making a holiday visit to China and visiting the site of her mother’s birth and her grandfather’s death, as related in the prologue in Friends of Sir Robert Hart. She can be contacted at email@example.com or visited at Twitter, or at Facebook.