On leaving the British Army, Dolphin founded a number of companies, including the Corgi Motorcycle Co Ltd. in 1946 and also set up Dolphin Industrial Developments Ltd and Hydraulic Developments Ltd, which he ran until 1950, when he became Chief Engineer at the Atomic Weapons Research Establishment. Dolphin then went on to become Engineer-in-Chief at the United Kingdom Atomic Energy Authority Research Group until 1959, became joint Managing Director of Lansing Bagnall Ltd and J. E. Shay Ltd until 1964, and a Director of TI (Group Services) Ltd, where he successfully secured patents for a number of inventions, including sheet piling revetments, improvements to fork lift trucks and the forerunner of the modern mobility scooter.
