This analysis examines the precarious status of the Ecumenical Patriarchate of Constantinople following the 1923 Treaty of Lausanne. It demonstrates that while the Treaty’s provisions on minority rights (Articles 37–45) provided a general legal framework, the specific survival of the Patriarchate was secured by a distinct political bargain, not a Treaty article. British diplomacy, spearheaded by Lord Curzon, played a critical role along with the other parties in this outcome, successfully opposing Turkey’s initial demand for abolition. The compromise extracted a Turkish pledge to allow the institution to remain, contingent upon its renunciation of all political authority, transforming it into a purely religious entity. The subsequent 1925 House of Lords debate, provoked by Turkey’s expulsion of Patriarch Constantine VI, reveals that Britain’s commitment to the Patriarchate was multifaceted. It was driven not merely by religious sympathy but by core strategic interests: upholding the credibility of the Lausanne settlement, maintaining regional stability in the Eastern Mediterranean, and protecting Britain’s diplomatic prestige as a guarantor of international agreements. The debate crystallised the central post-Lausanne tension between the principle of absolute national sovereignty, which Turkey invoked, and the weight of political commitments made to the international community. Ultimately, the Patriarchate’s survival illustrates the fragile and conditional nature of minority protections under the treaty. Its history became a barometer for Turkey’s adherence to the spirit of Lausanne and exposed the limits of international guarantees in the face of assertive nationalist sovereignty, a dynamic that continues to shape the institution’s contested status in modern Turkey.