He went to London University where he met his future wife Sheila, with whom he had four children (Christopher, Hilary, Timothy and Nicola).
After graduating Jenkinson joined the Royal Air Force (RAF) in 1956, from which he retired in 1972 having achieved the rank of Squadron Leader.
Soon after the Science Museum was asked to take on the historic railway collections, David, having retired from the RAF, applied for and was appointed as an education officer with the Science Museum at South Kensington, where he worked with John Van Riemsdijk on the layout of the new building in York.
He put some of the time thus freed into his writing career and was editor of BackTrack from 1989 to 1994, in succession to the magazine's founder, Nigel Trevena, of Atlantic Transport Publishers.
[6] In the year he left the RAF he started his layout Little Long Drag, which incorporated Garsdale Road and a lengthy run in a custom-built shed.