This paper assesses the role played by the League of Nations’ Permanent Mandates Commission (PMC) in ensuring that the promises made in the Balfour Declaration could not easily be rescinded during the interwar period, despite the growing troubles on the ground. It begins by charting British administrators’ responses (in Palestine and in the Colonial Office in London) to the Balfour Declaration: left to deal with the consequences of a promise that gave rise to clearly irreconcilable demands, the response of British officials who were left to hold the balance was marked by increasing frustration, ranging from initial tolerance to outright hostility, with what was increasingly seen as a terrible misjudgement. Yet, no change of policy was made. In identifying why, this paper starts from the premise that “the drafting of the [League of Nations] mandate was an act of far greater importance than the drafting of the Balfour Declaration” (Yapp,329). Once the Balfour Declaration was written into the terms of the 1923 League of Nations mandate that sanctioned British rule in Palestine, it turned one of several competing wartime promises into a binding contract mediated by the League of Nations. Restrained in this way, British officials found it very problematic to ever consider changing the terms of the mandate, and rescinding the Balfour Declaration, however obvious the misjudgement. To be sure Palestine operated very much as a typical colony, but the mandate system differed from prewar imperialism in the extent that Britain remained fettered by an institution that placed the Palestine administration in the court of international public opinion. The PMC may have done little to constrain officials in their day-to-day running of Palestine, but it was nonetheless a forum in which the colonial powers’ prestige was at stake. Rather than simply dismissing a war-time promise, the process of changing the terms of the mandate would require, as one official fretted, “going in to the dock” in Geneva, “while the French representatives sit there smirking.” At worst, this would “open the gates to French or other intrusion” (Fieldhouse, 218), at a time when British defence remained strategically committed to remaining in Palestine. As the leading official in the Colonial Office Sir John Shuckburgh admitted in 1929, "the balance of advantage lies in doing nothing.” M. Yapp, The Making of the Modern Near East, 1792-1923 (Longman, 1987). D.K. Fieldhouse, Western Imperialism in the Middle East (Oxford, 2006).