Career
His academic career was based at the University of Leicester, where he held the post of Professor of Plant taxonomy. He is a past president of the Botanical Society of Britain and Ireland. He has also been responsible for a number of notable publications relating to the vascular plant flora of Britain and Ireland:
Hybridization and the flora of the British Isles
New Flora of the British Isles
Vice-county Census Catalogue of the Vascular Plants of Great Britain
He also wrote the student textbook Plant Taxonomy and Biosystematics.