Johnson was born 9 March 1915 in Barrow upon Soar, Leicestershire, to Alfred Johnson and Beatrice May Johnson. He lived and was brought up in Melton Mowbray, where his father was a policeman. Alfred Johnson was an Inspector by the mid-1930s. One evening Oswald Mosley, the leader of the British Union of Fascists, held a meeting in the town. The license for the meeting expired at 22:00 at which time Alfred Johnson went alone and ejected the Fascists from the building.