David trained in the biology of ageing using model organisms, especially the nematode worm C. elegans. He has found that certain bacteria accelerate ageing. He is a Professor in the Biology of Ageing at Durham University and since 2022 Chair of the British Society for Research on Ageing, a learned Society and Charity. In 2018, he co-founded the company Magnitude Biosciences that provides research in ageing to companies globally and helps them find new interventions to maintain health.