In 1908, Hankey was appointed Naval Assistant Secretary to the
Committee of Imperial Defence. He became Secretary to the Committee in 1912, a position that he would hold for 26 years. In November 1914, he took on the additional duty of Secretary of the War Council. In that function, he took notice of the ideas of Major
Ernest Swinton to build a tracked armoured vehicle and brought them to the attention of
Winston Churchill on 25 December 1914. This led to the eventual creation of the
Landship Committee. In December 1916,
David Lloyd George became
Prime Minister and greatly changed how the government was run. A small
War Cabinet was instigated, and Hankey was appointed as its Secretary and served as Secretary of the
Imperial War Cabinet, which also incorporated representatives of the Colonies and Dominion governments. He gained such a reputation for strong competence that when the full Cabinet was restored in 1919, the secretariat was retained, and Hankey then served as Secretary to the Cabinet for 19 years. In 1923, he acquired the further position of Clerk of the
Privy Council. During his long tenure, he would also often serve as British Secretary to many international conferences and Secretary-General of many Imperial Conferences.
John Cairncross, one of the
Cambridge Spies, briefly served as his secretary. In August 1938, Hankey retired from government and became a British Government Director of the
Suez Canal Company, a post that he would hold for only one year. Hankey remained a respected figure and was often consulted by ministers and civil servants for advice. In August 1939, he advised
Neville Chamberlain about the formation of a new
War Cabinet and, the following month, became another of Chamberlain's many non-party political appointments when he was made
Minister without Portfolio and a member of the
War Cabinet. Hankey was reluctant to take on the task but agreed to do so. He became
Chancellor of the Duchy of Lancaster when Chamberlain was succeeded by
Winston Churchill in May 1940 but was left out of Churchill's War Cabinet. In July 1941, Lord Hankey was moved to the position of
Paymaster General, but the following year, he was dropped from the government altogether. He continued to hold other positions in both the public and private sectors until his death. ==Post-war writings==