He was a son of the 3rd Marquise of Salisbury, head of the foreign office in Benjamin Disreali’s government and thrice prime minister. Lord Cecil was first educated at home and later went on to study law at Oxford. In 1887 he launched his barrister’s practice. In 1906 he was elected a conservative member of parliament.

During World War I and in the years 1916-22, Cecil was under-secretary of state for foreign affairs. From 1916 to 1918 he was also Minister of Blockade whose task was to exert economic pressure on the countries at war with Great Britain. Influenced by the cruelty and damage caused by the war, he became convinced that civilisation could only survive if it could devise an international peace-keeping system. In 1916 he presented a memorandum containing advice on how to avoid war.

He was responsible for the negotiations on the creation of the League of Nations at the Paris Peace Conference and later gave nearly 30 years of his life to the League. In 1923, after receiving the title of Lord Viscount Chelwood, Cecil became a member of the House of Lords and in 1924 took the ministerial post of the Chancellor of the Duchy of Lancaster, reporting to the head of diplomacy and responsible for all issues related to the League of Nations. In 1927, disappointed with his government’s approach to the League, he resigned from his ministerial post, but still remained the official British delegate until 1932. He presided over the British League of Nations (1923-1945) and was one of the initiators of the international Peace Campaign, as well as its President. He wrote on issues of peace and the League of Nations.