Johnson is a retired local government officer[2] who lives in Leicester.
[3] Johnson is known for his "meticulous research into all aspects of the [Ffestiniog] railway’s operation".
[3] He was a director of the Ffestiniog Railway Society from 1991 to 2003 and editor (originally jointly with Norman Gurley and Dan Wilson) of the Festiniog Railway Society Magazine from 1974 to 2003.
[2] From June 1995 until Match 2019, Johnson contributed a monthly column of narrow gauge railway news for Steam Railway magazine; as of September 2017 he was the magazine's longest serving continuous contributor.
[5] Since 2006 he has written obituaries of prominent railway people for The Guardian newspaper.