Great-grandson of a crofter and son-in-law of a Duke, Harold Macmillan (1894-1986) was both complex as a person and influential as a politican. Marked by terrible experiences in the trenches in the First World War and by his work as an MP during the Depression, he was a Tory rebel - an outspoken backbencher, opposing the economic policies of the 1930s and the appeasement policies of his own government.

Churchill gave him responsibility during the Second World War with executive command as 'Viceroy of the Mediterranean'. After the War, in opposition, Macmillan was one of the principal...