He attended Morrison's Academy in the town, interrupting his education to join the Royal Artillery and serve in the First World War.

In the 1924 general election he fought Derby as the sole Liberal candidate, opposing J. H. Thomas who was a senior Labour Minister.

[citation needed] In January 1933, Henderson-Stewart was adopted as Liberal National candidate for East Fife, where the death of the sitting Member of Parliament Sir James Duncan Millar had precipitated a by-election.

[8] He gained a reputation for diligent constituency work, among the farmers and fishermen of Fife, and soon after his election opposed a reduction in the grant to the Forestry Commission which he considered a false economy.

On foreign affairs, he spoke in 1934 in favour of the United Kingdom staying out of any conflict between France and Germany;[9] that July he stated that the innermost chamber of world peace lay in Anglo-American friendship.

[12] In March 1939 he was a co-signatory of a Parliamentary motion put forward by Anthony Eden and Winston Churchill which called for a National government "on the widest possible basis" to enable Britain to put forward its maximum military effort; the motion was not welcomed by the Chamberlain government.

When Parliament reassembled after the election, Henderson-Stewart was chosen as the Chairman of the Liberal National Parliamentary Party for the session.

[23] The Conservatives' return to power in 1951 led to Henderson-Stewart's appointment as Joint Parliamentary Under-Secretary of State at the Scottish Office in February 1952.

In August of that year he was invited to speak to the European Youth Conference in Midlothian, at which he declared that "the mother country of a great Commonwealth and Empire" could not surrender vital elements of sovereignty.

[29] He was created Baronet of Callumshill in the County of Perth on 28 March 1957;[30] the Court of the Lord Lyon granted a warrant allowing him to change his surname to Henderson-Stewart (and by Deed Poll).