His 1938 diplomatic mission to Czechoslovakia was key to the enactment of the British policy of appeasement of Nazi Germany preceding the Second World War.

[9] He was one of the small group, that included Reginald McKenna, who believed in sound public finances;[citation needed] they had witnessed the lax administration of the Chief Secretary for Ireland.

[clarification needed] Runciman, along with McKenna and Lord Haldane, pressured Prime Minister H. H. Asquith to reject Chancellor of the Exchequer David Lloyd George's 1910 People's Budget raising taxes on the landed aristocracy and upper class to pay for welfare programs.

Runciman encouraged political dialogue, socialism, and James Larkin's movement in Ireland, which the cabinet swiftly sought to decriminalise.

Runciman was also sympathetic to addressing issues concerning rural areas,[16] such as improved wages for agricultural labourers[17] and the provision of housing.

[18] In 1914, on the British entry into World War I, the President of the Board of Trade, John Burns, resigned and on Sunday 2 August Runciman was appointed to succeed him.

[19] Runciman was wholly sympathetic to Lloyd George's proposal to actively intervene in union wage disputes since "men were not malingering, but worn out...".

[20] Runciman encouraged Kitchener at dinner to remove Sir John French from command of the British Expeditionary Force (BEF).

In May 1915, after seeking Sir Edward Grey's counsel at the Foreign Office, Runciman agreed to serve in Asquith's new coalition government.

However, Runciman continued to enjoy good relations with the Chancellor because they shared the aims of improving trade receipts, reducing debt, and increasing output.

[27] The Liberals soon found themselves heavily divided over how to respond to the Great Depression, whether or not to continue supporting the Labour government of Ramsay MacDonald and even over the basic direction of the party.

Further division emerged, however, when it was proposed that the National Government call a general election to seek a mandate to introduce protective tariffs, a policy that was anathema to Runciman and many other Liberals.

It was felt prudent to balance the key Cabinet committee that would take the decisions on tariffs; and so Runciman was appointed President of the Board of Trade once more, in the belief that he would serve as a counterbalance to the protectionist Chancellor of the Exchequer Neville Chamberlain.

He concluded the Roca-Runciman Treaty with Argentina (one of the events of the Infamous Decade), initiated by that country to avoid the curtailment of Argentine beef imports.

Unknown to Runciman, the SdP, which ostensibly called for autonomy for the Sudetenland, followed instructions from Nazi Germany not to reach any agreement on the matter, and thus the attempts at mediation failed.

[32] The published outcome of the mission, known as the Runciman Report, was issued by the mediator on 21 September 1938 in the form of letters addressed to Neville Chamberlain and Edvard Beneš, the President of Czechoslovakia.

Runciman considered the actions of the Czechoslovak authorities to be "not actively oppressive, and certainly not 'terroristic'" but "marked by tactlessness, lack of understanding, petty intolerance and discrimination".

Archival evidence suggests that the recommendations of the Runciman Report were amended at a late stage of the drafting to provide justification for Chamberlain's policy of territorial transfer.

That was spent mostly but not entirely on the country estates of members of the SdP-supporting Sudeten German aristocracy in a social and political environment hostile to the Czechoslovak government.