He was a junior reporter at the North West Evening Mail in Barrow-in-Furness from 1965 to 1966. One of the duties of news staff was to cover sport, which was an unwelcome intrusion into the weekend. Johnson once reported the score of a Barrow Rugby League match inaccurately and was cursed as a bloody fool by his editor on the Monday morning. However, he never had to cover sport again.
He was the editor of the conservative Spectator magazine from 1995 to 1999 and was a popular columnist for The Daily Telegraph. He had a particular reputation for his work as a parliamentary sketch writer, as which he was widely regarded as the most incisive and amusing commentator of his generation.