Randolph graduated from the University of Sydney in 1991. After graduating, he worked part-time in Australia and the UK while pursuing a career as a professional triathlete. In 1997, he started Paddington Cat Hospital with his wife, Melissa Catt. Randolph achieved Membership of the Australian College of Veterinary Scientists in Medicine of Cats in 2001, and his clinical pathology PhD in 2015. He has been an official consultant VIN consultant since 2001. Randolph has published more than 60 peer-reviewed papers and was a co-editor of both editions of the internal medicine section of Susan Little’s The Cat: Clinical Medicine and Management for which he wrote twelve chapters in diverse areas. Randolph administers the vetbiologicalvariation.org website; he became a founding director of CustomClinPath software in 2021. He used to keep fit with cycling, loves learning languages, speaking passable French and rudimentary Polish.