During which years was the British statesman, for which Knox Cunningham was Parliamentary Private Secretary, Prime Minister of the United Kingdom?
Knox Cunningham:  As an Ulster Unionist politician at a time when the Unionists were part of the Conservative Party, he was also a significant figure in United Kingdom politics as Parliamentary Private Secretary to Harold Macmillan. Harold Macmillan: Maurice Harold Macmillan, 1st Earl of Stockton, {'1': ", '2': ", '3': ", '4': "} (10 February 1894 – 29 December 1986) was a British statesman of the Conservative Party who served as Prime Minister of the United Kingdom from 1957 to 1963.
1957 to 1963