How do states’ desires to perform an international-societal role interact with the imperative to safeguard their security in an anarchic international system? Using the case of the contemporary United Kingdom, this article explores the tensions between roleplay and realpolitik—gaining social recognition as a particular kind of state while doing what it takes to survive—through one key role conception, “Great Power.” Recent scholarship has dubbed Britain a “residual Great Power”: lacking the wherewithal to impose regional order through preponderance, it is still cast into the role of militarized international order-upholder by the allies whose support is necessary for such role-sustainment, America and France. Yet this role-based approach sets a different threshold on capability than the requirement to undertake survival-essential military missions, independent of potentially unreliable allies’ charity—realists’ understanding of “great power.” Theoretically, therefore, the article demonstrates that roleplay and realpolitik remain separate incentive structures underlying states’ foreign policy choices. Empirically, meanwhile, the article shows—through opportunity-cost force-posture analysis—that contemporary Britain is torn between the logics. Striving for independent self-protection capabilities, above-and-beyond the “residual power” criterion, London nonetheless makes a residual power's implicit assumptions about alliance support in the deployment of those capabilities.