Following graduation from Cambridge University in 2000, Harry spent 2 years in mixed practice and then 3 years at Liphook equine Hospital, where he developed an interest in internal medicine. He then worked for 6 years at Massey University, New Zealand, first as resident and then as lecturer in equine internal medicine. He was also team vet for the New Zealand 3-day eventing development squad. On returning to the UK in 2011 Harry worked for 18 months at Fellowes Farm equine clinic, before being appointed as Lecturer in equine medicine at Leahurst in 2013.

He became a Diplomat of the American college of veterinary internal medicine in 2010, and an RCVS recognised specialist in equine medicine in 2014. He is interested in all areas of equine internal medicine, but has particular interests in endocrinology, gastroenterology and imaging. He was awarded a PhD in equine endocrinology in 2022.