Donald McIntosh Johnson (17 February 1903 – 5 November 1978) was a British general practitioner, author and politician who was a member of parliament for nine years. He regarded himself as a 'Cassandra' (one whose prophecies were true but never believed), and he was described by one observer as "an eccentric man of considerable personal charm and egotistical obstinacy" who had failed to prove it was possible to be both a Conservative and Independent MP at the same time.
Johnson was from a Lancashire family and was sent to Cheltenham College (an Independent school), where he did well, and Gonville and Caius College, Cambridge, where he read medicine and obtained a first class honours degree. Interested in entering the profession of medicine, he went on to St Bartholomew's Hospital on an Entrance Scholarship.
Donald Johnson was married twice and fathered three children, two boys and a girl (Carol). His second wife, Betty, whom he met at the Marlborough Arms (see below), died in 1979.
In 1926 Johnson qualified as a doctor. His first medical job was as Medical Officer on the Cambridge University East Greenland Expedition of 1926; when he returned, he took up the post of Casualty Officer at the Metropolitan Hospital in London. In 1927 he was House Physician at the East London Hospital for Children. In 1928, his love of travel having again taken him away from Britain, he was Medical Officer to the Harrington Harbour Hospital in Quebec, which was run by the International Grenfell Association, a charity.
Johnson returned to become a General Practitioner at Thornton Heath in Croydon, south London, from 1930. In that year he was also called to the Bar, although he never practised. He became interested in politics and active in the Liberal Party, and in the 1935 general election he was the Liberal Party's candidate in Bury.