He began his research career in 1996 in Exeter in the field of monogenic forms of diabetes. His work, as a PhD student with Prof Andrew Hattersley, played a key role in the characterization of the genes for maturity onset diabetes of the young. Key work prior to the genome wide association studies includes some of the first use of meta-analyses and multiple replication studies to determine the role of common variants in disease. These include the assessment of common variants in the KCNJ11 (E23K variant, Diabetes 2003) gene in type 2 diabetes risk and the identification of the first robust associations between common variants and birth weight (TCF7L2 and Glucokinase, AJHG 2006 & 2007).

Broad research specialisms
He and his colleagues focus on using genome wide approaches to identify genetic variation associated with common human disease and quantitative phenotypes and translating that knowledge into an improved understanding of disease biology.

They are members of several large collaborations that are continuing to identify more variants in the human genome that influence important human traits. They are translating these genetic associations into an improved understanding of the biological basis of disease and normal physiology. Examples include Mendelian Randomization studies that provide evidence for a role of sex-hormones in type 2 diabetes, links between fetal growth and type 2 diabetes, and, genetic variants that increase adiposity but lower risk of metabolic diseases.