 He is recognised as one of the leading experts in the history of medieval England.Nigel Saul has written numerous books including "Knights and Esquires, The Gloucestershire Gentry in the Fourteenth Century" (Oxford, 1981), and "The Oxford Illustrated History of Medieval England" (Oxford, 1997).His major biography "Richard II" (Yale, 1997) was the product of ten years' work and was acclaimed by P. D. James as "unlikely to be surpassed in scholarship, comprehensiveness, or in the biographer's insight into his subject's character".