He was President of the National Union of Students from 1927 to 1929. He was Liberal candidate for the Ipswich Division of Suffolk at the 1929 general election. He was Liberal candidate for the King's Lynn Division of Norfolk at the 1935 general election. After the election he was adopted by Dorset East Liberal Association as their prospective parliamentary candidate, a more winnable seat as the Liberals came second in 1935 and had last won as recently as 1929. Darvall was prominent touring around Britain giving a series of lectures on world affairs in conjunction with the University Extension Association. Darvall was elected to the influential policy-making body the Liberal Party Council. From this platform he was one of the leading figures in the party who argued in support of a Popular Front which was also argued for inside the Labour party by the likes of Sir Stafford Cripps. A Popular Front government would most likely come to power as a result of electoral co-operation between the Liberal and Labour parties. A general election was expected to take place sometime in 1939. In February 1939, while Cripps was being threatened by the Labour party with expulsion, Darvall was told by friends in the Labour party that the rejection of Cripps' Popular Front strategy did not mean that locally agreed electoral co-operation could not go ahead. Darvall advised Liberal HQ to refrain from publicly backing Cripps as this could help secure more local electoral pacts. Although Labour had already selected a prospective parliamentary candidate for Dorset East, it was indicated that they would be prepared to withdraw him and support Darvall in a general election. However, in July 1939 Darvall was approached and agreed to stand as the Liberal candidate for the 1939 Hythe by-election in Kent. The Liberals were also the main challengers to the Conservatives in Hythe and Darvall had received an assurance that Labour would not oppose him in Hythe. Although Darvall achieved a swing to the Liberals of 8.4%, the Conservatives held the seat. With a general election perhaps only a couple of months away, Darvall agreed to remain as Liberal candidate for Hythe and the Dorset East Liberals quickly found a replacement for him in D. Graham Hutton. As things transpired, the anticipated general election was not held due to the outbreak of war.
He was British Consul, Denver, 1945–46; 1st Secretary HM Embassy, Washington, 1946–49; Vice-Chairman Kinsman Trust, 1949–56; Editor, The English-Speaking World, 1950–53; Director-General, English-speaking Union of the Commonwealth, 1949–57; Chairman, Congress of European-American Assoc., 1954–57. European Editor, World Review, 1958–59. Hon. Dir, UK Committee, Atlantic Congress, 1959; Attached British High Commission, Cyprus, 1960–62; Dir, British Information Services, Eastern Caribbean, 1962–66; attached, British Consulate-Gen., Barcelona, 1966; Consul, Boston, 1966–68; FCO, 1968–70. He retired from HM Diplomatic Service in 1970. He was Dean of Academics, Alvescot College, 1970–71, Vice-Pres., 1971–72.
Publications
He wrote extensively throughout his career, but his three most significant works were;
Popular Disturbances and Public Order in Regency England, 1934
