Dai Rees was a chemist and science administrator who conducted important work on the structure of carbohydrates. As organic molecules that play an important role in cell function, Dai's research in this area has been of considerable biological importance.
As a research scientist for Unilever in the 1970s, Dai contributed to an improved understanding of the behaviour of polysaccharides in solution. There he discovered that these long carbohydrate chains could be used to stiffen fluids - work of considerable value in the manufacture and characterisation of food.
After being appointed to run Unilever's bioscience research programme, Dai was chosen as the fifth director of the National Institute of Medical Research. In this role from 1982 to 1987, he helped reorganise the institute and greatly enhanced its ability to collaborate with industry. A well-respected leader in the scientific community, Dai later served as Secretary of the Medical Research Council and as President of the European Science Foundation. He was knighted in 1993 for his services to science.