Johnson was educated at Camden Street Junior School and Loughborough Grammar School. Johnson's uncle, Edgar Charles Rossell, who had won the Military Cross with the Royal Fusiliers in 1916, paid for Johnson's education at Loughborough. According to his brother Ross, during his time there, Johnson was nearly expelled after refusing punishment for a misdemeanour, believing it to be unjustified: "he was very principled and simply dug his heels in". Among Johnson's hobbies and interests were shooting and sports; he shot rabbits and birds in the local countryside.